diff --git a/docs/your-first-package.md b/docs/your-first-package.md
index 02cb98379..fe9550bd9 100644
--- a/docs/your-first-package.md
+++ b/docs/your-first-package.md
@@ -53,7 +53,7 @@ module.exports =
 
   convert: ->
     # This assumes the active pane item is an editor
-    editor = atom.workspace.activePaneItem
+    editor = atom.workspace.getActivePaneItem()
     editor.insertText('Hello, World!')
 ```
 
@@ -131,7 +131,7 @@ inserting 'Hello, World!' convert the selected text to ASCII art.
 ```coffeescript
 convert: ->
   # This assumes the active pane item is an editor
-  editor = atom.workspace.activePaneItem
+  editor = atom.workspace.getActivePaneItem()
   selection = editor.getLastSelection()
 
   figlet = require 'figlet'
diff --git a/package.json b/package.json
index d24ca30de..6dc56fa54 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,8 @@
     "coffee-script": "1.7.0",
     "coffeestack": "0.7.0",
     "delegato": "^1",
-    "emissary": "^1.2.2",
+    "emissary": "^1.3.1",
+    "event-kit": "0.5.0",
     "first-mate": "^2.0.5",
     "fs-plus": "^2.2.6",
     "fstream": "0.1.24",
@@ -109,7 +110,6 @@
     "welcome": "0.18.0",
     "whitespace": "0.25.0",
     "wrap-guide": "0.21.0",
-
     "language-c": "0.28.0",
     "language-coffee-script": "0.30.0",
     "language-css": "0.17.0",
diff --git a/spec/pane-container-spec.coffee b/spec/pane-container-spec.coffee
index df9921e69..1701e3f03 100644
--- a/spec/pane-container-spec.coffee
+++ b/spec/pane-container-spec.coffee
@@ -27,42 +27,91 @@ describe "PaneContainer", ->
 
     it "preserves the active pane across serialization, independent of focus", ->
       pane3A.activate()
-      expect(containerA.activePane).toBe pane3A
+      expect(containerA.getActivePane()).toBe pane3A
 
       containerB = containerA.testSerialization()
       [pane1B, pane2B, pane3B] = containerB.getPanes()
-      expect(containerB.activePane).toBe pane3B
+      expect(containerB.getActivePane()).toBe pane3B
 
-  describe "::activePane", ->
+  it "does not allow the root pane to be destroyed", ->
+    container = new PaneContainer
+    container.getRoot().destroy()
+    expect(container.getRoot()).toBeDefined()
+    expect(container.getRoot().isDestroyed()).toBe false
+
+  describe "::getActivePane()", ->
     [container, pane1, pane2] = []
 
     beforeEach ->
       container = new PaneContainer
-      pane1 = container.root
+      pane1 = container.getRoot()
 
-    it "references the first pane if no pane has been made active", ->
-      expect(container.activePane).toBe pane1
-      expect(pane1.active).toBe true
+    it "returns the first pane if no pane has been made active", ->
+      expect(container.getActivePane()).toBe pane1
+      expect(pane1.isActive()).toBe true
 
-    it "references the most pane on which ::activate was most recently called", ->
+    it "returns the most pane on which ::activate() was most recently called", ->
       pane2 = pane1.splitRight()
       pane2.activate()
-      expect(container.activePane).toBe pane2
-      expect(pane1.active).toBe false
-      expect(pane2.active).toBe true
+      expect(container.getActivePane()).toBe pane2
+      expect(pane1.isActive()).toBe false
+      expect(pane2.isActive()).toBe true
       pane1.activate()
-      expect(container.activePane).toBe pane1
-      expect(pane1.active).toBe true
-      expect(pane2.active).toBe false
+      expect(container.getActivePane()).toBe pane1
+      expect(pane1.isActive()).toBe true
+      expect(pane2.isActive()).toBe false
 
-    it "is reassigned to the next pane if the current active pane is destroyed", ->
+    it "returns the next pane if the current active pane is destroyed", ->
       pane2 = pane1.splitRight()
       pane2.activate()
       pane2.destroy()
-      expect(container.activePane).toBe pane1
-      expect(pane1.active).toBe true
+      expect(container.getActivePane()).toBe pane1
+      expect(pane1.isActive()).toBe true
 
-    it "does not allow the root pane to be destroyed", ->
-      pane1.destroy()
-      expect(container.root).toBe pane1
-      expect(pane1.isDestroyed()).toBe false
+  describe "::onDidChangeActivePaneItem()", ->
+    [container, pane1, pane2, observed] = []
+
+    beforeEach ->
+      container = new PaneContainer(root: new Pane(items: [new Object, new Object]))
+      container.getRoot().splitRight(items: [new Object, new Object])
+      [pane1, pane2] = container.getPanes()
+
+      observed = []
+      container.onDidChangeActivePaneItem (item) -> observed.push(item)
+
+    it "invokes observers when the active item of the active pane changes", ->
+      pane2.activateNextItem()
+      pane2.activateNextItem()
+      expect(observed).toEqual [pane2.itemAtIndex(1), pane2.itemAtIndex(0)]
+
+    it "invokes observers when the active pane changes", ->
+      pane1.activate()
+      pane2.activate()
+      expect(observed).toEqual [pane1.itemAtIndex(0), pane2.itemAtIndex(0)]
+
+  describe "::observePanes()", ->
+    it "invokes observers with all current and future panes", ->
+      container = new PaneContainer
+      container.getRoot().splitRight()
+      [pane1, pane2] = container.getPanes()
+
+      observed = []
+      container.observePanes (pane) -> observed.push(pane)
+
+      pane3 = pane2.splitDown()
+      pane4 = pane2.splitRight()
+
+      expect(observed).toEqual [pane1, pane2, pane3, pane4]
+
+  describe "::observePaneItems()", ->
+    it "invokes observers with all current and future pane items", ->
+      container = new PaneContainer(root: new Pane(items: [new Object, new Object]))
+      container.getRoot().splitRight(items: [new Object])
+      [pane1, pane2] = container.getPanes()
+      observed = []
+      container.observePaneItems (pane) -> observed.push(pane)
+
+      pane3 = pane2.splitDown(items: [new Object])
+      pane3.addItems([new Object, new Object])
+
+      expect(observed).toEqual container.getPaneItems()
diff --git a/spec/pane-spec.coffee b/spec/pane-spec.coffee
index 04b1c2474..c66b88850 100644
--- a/spec/pane-spec.coffee
+++ b/spec/pane-spec.coffee
@@ -21,39 +21,83 @@ describe "Pane", ->
   describe "construction", ->
     it "sets the active item to the first item", ->
       pane = new Pane(items: [new Item("A"), new Item("B")])
-      expect(pane.activeItem).toBe pane.items[0]
+      expect(pane.getActiveItem()).toBe pane.itemAtIndex(0)
 
     it "compacts the items array", ->
       pane = new Pane(items: [undefined, new Item("A"), null, new Item("B")])
-      expect(pane.items.length).toBe 2
-      expect(pane.activeItem).toBe pane.items[0]
+      expect(pane.getItems().length).toBe 2
+      expect(pane.getActiveItem()).toBe pane.itemAtIndex(0)
+
+  describe "::activate()", ->
+    [container, pane1, pane2] = []
+
+    beforeEach ->
+      container = new PaneContainer(root: new Pane)
+      container.getRoot().splitRight()
+      [pane1, pane2] = container.getPanes()
+
+    it "changes the active pane on the container", ->
+      expect(container.getActivePane()).toBe pane2
+      pane1.activate()
+      expect(container.getActivePane()).toBe pane1
+      pane2.activate()
+      expect(container.getActivePane()).toBe pane2
+
+    it "invokes ::onDidChangeActivePane observers on the container", ->
+      observed = []
+      container.onDidChangeActivePane (activePane) -> observed.push(activePane)
+
+      pane1.activate()
+      pane1.activate()
+      pane2.activate()
+      pane1.activate()
+      expect(observed).toEqual [pane1, pane2, pane1]
+
+    it "invokes ::onDidChangeActive observers on the relevant panes", ->
+      observed = []
+      pane1.onDidChangeActive (active) -> observed.push(active)
+      pane1.activate()
+      pane2.activate()
+      expect(observed).toEqual [true, false]
+
+    it "invokes ::onDidActivate() observers", ->
+      eventCount = 0
+      pane1.onDidActivate -> eventCount++
+      pane1.activate()
+      pane1.activate()
+      pane2.activate()
+      expect(eventCount).toBe 2
 
   describe "::addItem(item, index)", ->
     it "adds the item at the given index", ->
       pane = new Pane(items: [new Item("A"), new Item("B")])
-      [item1, item2] = pane.items
+      [item1, item2] = pane.getItems()
       item3 = new Item("C")
       pane.addItem(item3, 1)
-      expect(pane.items).toEqual [item1, item3, item2]
+      expect(pane.getItems()).toEqual [item1, item3, item2]
 
-    it "adds the item after the active item ", ->
+    it "adds the item after the active item if no index is provided", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
       pane.activateItem(item2)
       item4 = new Item("D")
       pane.addItem(item4)
-      expect(pane.items).toEqual [item1, item2, item4, item3]
+      expect(pane.getItems()).toEqual [item1, item2, item4, item3]
 
     it "sets the active item after adding the first item", ->
       pane = new Pane
       item = new Item("A")
-      events = []
-      pane.on 'item-added', -> events.push('item-added')
-      pane.$activeItem.changes.onValue -> events.push('active-item-changed')
-
       pane.addItem(item)
-      expect(pane.activeItem).toBe item
-      expect(events).toEqual ['item-added', 'active-item-changed']
+      expect(pane.getActiveItem()).toBe item
+
+    it "invokes ::onDidAddItem() observers", ->
+      pane = new Pane(items: [new Item("A"), new Item("B")])
+      events = []
+      pane.onDidAddItem (event) -> events.push(event)
+
+      item = new Item("C")
+      pane.addItem(item, 1)
+      expect(events).toEqual [{item, index: 1}]
 
   describe "::activateItem(item)", ->
     pane = null
@@ -62,83 +106,102 @@ describe "Pane", ->
       pane = new Pane(items: [new Item("A"), new Item("B")])
 
     it "changes the active item to the current item", ->
-      expect(pane.activeItem).toBe pane.items[0]
-      pane.activateItem(pane.items[1])
-      expect(pane.activeItem).toBe pane.items[1]
+      expect(pane.getActiveItem()).toBe pane.itemAtIndex(0)
+      pane.activateItem(pane.itemAtIndex(1))
+      expect(pane.getActiveItem()).toBe pane.itemAtIndex(1)
 
     it "adds the given item if it isn't present in ::items", ->
       item = new Item("C")
       pane.activateItem(item)
-      expect(item in pane.items).toBe true
-      expect(pane.activeItem).toBe item
+      expect(item in pane.getItems()).toBe true
+      expect(pane.getActiveItem()).toBe item
+
+    it "invokes ::onDidChangeActiveItem() observers", ->
+      observed = []
+      pane.onDidChangeActiveItem (item) -> observed.push(item)
+      pane.activateItem(pane.itemAtIndex(1))
+      expect(observed).toEqual [pane.itemAtIndex(1)]
 
   describe "::activateNextItem() and ::activatePreviousItem()", ->
     it "sets the active item to the next/previous item, looping around at either end", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
 
-      expect(pane.activeItem).toBe item1
+      expect(pane.getActiveItem()).toBe item1
       pane.activatePreviousItem()
-      expect(pane.activeItem).toBe item3
+      expect(pane.getActiveItem()).toBe item3
       pane.activatePreviousItem()
-      expect(pane.activeItem).toBe item2
+      expect(pane.getActiveItem()).toBe item2
       pane.activateNextItem()
-      expect(pane.activeItem).toBe item3
+      expect(pane.getActiveItem()).toBe item3
       pane.activateNextItem()
-      expect(pane.activeItem).toBe item1
+      expect(pane.getActiveItem()).toBe item1
 
   describe "::activateItemAtIndex(index)", ->
     it "activates the item at the given index", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
       pane.activateItemAtIndex(2)
-      expect(pane.activeItem).toBe item3
+      expect(pane.getActiveItem()).toBe item3
       pane.activateItemAtIndex(1)
-      expect(pane.activeItem).toBe item2
+      expect(pane.getActiveItem()).toBe item2
       pane.activateItemAtIndex(0)
-      expect(pane.activeItem).toBe item1
+      expect(pane.getActiveItem()).toBe item1
 
       # Doesn't fail with out-of-bounds indices
       pane.activateItemAtIndex(100)
-      expect(pane.activeItem).toBe item1
+      expect(pane.getActiveItem()).toBe item1
       pane.activateItemAtIndex(-1)
-      expect(pane.activeItem).toBe item1
+      expect(pane.getActiveItem()).toBe item1
 
   describe "::destroyItem(item)", ->
     [pane, item1, item2, item3] = []
 
     beforeEach ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
 
-    it "removes the item from the items list", ->
-      expect(pane.activeItem).toBe item1
+    it "removes the item from the items list and destroyes it", ->
+      expect(pane.getActiveItem()).toBe item1
       pane.destroyItem(item2)
-      expect(item2 in pane.items).toBe false
-      expect(pane.activeItem).toBe item1
+      expect(item2 in pane.getItems()).toBe false
+      expect(item2.isDestroyed()).toBe true
+      expect(pane.getActiveItem()).toBe item1
 
       pane.destroyItem(item1)
-      expect(item1 in pane.items).toBe false
+      expect(item1 in pane.getItems()).toBe false
+      expect(item1.isDestroyed()).toBe true
+
+    it "invokes ::onWillDestroyItem() observers before destroying the item", ->
+      events = []
+      pane.onWillDestroyItem (event) ->
+        expect(item2.isDestroyed()).toBe false
+        events.push(event)
+
+      pane.destroyItem(item2)
+      expect(item2.isDestroyed()).toBe true
+      expect(events).toEqual [{item: item2, index: 1}]
+
+    it "invokes ::onDidRemoveItem() observers", ->
+      events = []
+      pane.onDidRemoveItem (event) -> events.push(event)
+      pane.destroyItem(item2)
+      expect(events).toEqual [{item: item2, index: 1, destroyed: true}]
 
     describe "when the destroyed item is the active item and is the first item", ->
       it "activates the next item", ->
-        expect(pane.activeItem).toBe item1
+        expect(pane.getActiveItem()).toBe item1
         pane.destroyItem(item1)
-        expect(pane.activeItem).toBe item2
+        expect(pane.getActiveItem()).toBe item2
 
     describe "when the destroyed item is the active item and is not the first item", ->
       beforeEach ->
         pane.activateItem(item2)
 
       it "activates the previous item", ->
-        expect(pane.activeItem).toBe item2
+        expect(pane.getActiveItem()).toBe item2
         pane.destroyItem(item2)
-        expect(pane.activeItem).toBe item1
-
-    it "emits 'item-removed' with the item, its index, and true indicating the item is being destroyed", ->
-      pane.on 'item-removed', itemRemovedHandler = jasmine.createSpy("itemRemovedHandler")
-      pane.destroyItem(item2)
-      expect(itemRemovedHandler).toHaveBeenCalledWith(item2, 1, true)
+        expect(pane.getActiveItem()).toBe item1
 
     describe "if the item is modified", ->
       itemUri = null
@@ -157,7 +220,7 @@ describe "Pane", ->
             pane.destroyItem(item1)
 
             expect(item1.save).toHaveBeenCalled()
-            expect(item1 in pane.items).toBe false
+            expect(item1 in pane.getItems()).toBe false
             expect(item1.isDestroyed()).toBe true
 
         describe "when the item has no uri", ->
@@ -170,7 +233,7 @@ describe "Pane", ->
 
             expect(atom.showSaveDialogSync).toHaveBeenCalled()
             expect(item1.saveAs).toHaveBeenCalledWith("/selected/path")
-            expect(item1 in pane.items).toBe false
+            expect(item1 in pane.getItems()).toBe false
             expect(item1.isDestroyed()).toBe true
 
       describe "if the [Don't Save] option is selected", ->
@@ -179,7 +242,7 @@ describe "Pane", ->
           pane.destroyItem(item1)
 
           expect(item1.save).not.toHaveBeenCalled()
-          expect(item1 in pane.items).toBe false
+          expect(item1 in pane.getItems()).toBe false
           expect(item1.isDestroyed()).toBe true
 
       describe "if the [Cancel] option is selected", ->
@@ -188,7 +251,7 @@ describe "Pane", ->
           pane.destroyItem(item1)
 
           expect(item1.save).not.toHaveBeenCalled()
-          expect(item1 in pane.items).toBe true
+          expect(item1 in pane.getItems()).toBe true
           expect(item1.isDestroyed()).toBe false
 
     describe "when the last item is destroyed", ->
@@ -197,7 +260,7 @@ describe "Pane", ->
           expect(atom.config.get('core.destroyEmptyPanes')).toBe false
           pane.destroyItem(item) for item in pane.getItems()
           expect(pane.isDestroyed()).toBe false
-          expect(pane.activeItem).toBeUndefined()
+          expect(pane.getActiveItem()).toBeUndefined()
           expect(-> pane.saveActiveItem()).not.toThrow()
           expect(-> pane.saveActiveItemAs()).not.toThrow()
 
@@ -210,10 +273,10 @@ describe "Pane", ->
   describe "::destroyActiveItem()", ->
     it "destroys the active item", ->
       pane = new Pane(items: [new Item("A"), new Item("B")])
-      activeItem = pane.activeItem
+      activeItem = pane.getActiveItem()
       pane.destroyActiveItem()
       expect(activeItem.isDestroyed()).toBe true
-      expect(activeItem in pane.items).toBe false
+      expect(activeItem in pane.getItems()).toBe false
 
     it "does not throw an exception if there are no more items", ->
       pane = new Pane
@@ -222,27 +285,40 @@ describe "Pane", ->
   describe "::destroyItems()", ->
     it "destroys all items", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
       pane.destroyItems()
       expect(item1.isDestroyed()).toBe true
       expect(item2.isDestroyed()).toBe true
       expect(item3.isDestroyed()).toBe true
-      expect(pane.items).toEqual []
+      expect(pane.getItems()).toEqual []
+
+  describe "::observeItems()", ->
+    it "invokes the observer with all current and future items", ->
+      pane = new Pane(items: [new Item, new Item])
+      [item1, item2] = pane.getItems()
+
+      observed = []
+      pane.observeItems (item) -> observed.push(item)
+
+      item3 = new Item
+      pane.addItem(item3)
+
+      expect(observed).toEqual [item1, item2, item3]
 
   describe "when an item emits a destroyed event", ->
     it "removes it from the list of items", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
-      pane.items[1].destroy()
-      expect(pane.items).toEqual [item1, item3]
+      [item1, item2, item3] = pane.getItems()
+      pane.itemAtIndex(1).destroy()
+      expect(pane.getItems()).toEqual [item1, item3]
 
   describe "::destroyInactiveItems()", ->
     it "destroys all items but the active item", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
       pane.activateItem(item2)
       pane.destroyInactiveItems()
-      expect(pane.items).toEqual [item2]
+      expect(pane.getItems()).toEqual [item2]
 
   describe "::saveActiveItem()", ->
     pane = null
@@ -253,30 +329,30 @@ describe "Pane", ->
 
     describe "when the active item has a uri", ->
       beforeEach ->
-        pane.activeItem.uri = "test"
+        pane.getActiveItem().uri = "test"
 
       describe "when the active item has a save method", ->
         it "saves the current item", ->
-          pane.activeItem.save = jasmine.createSpy("save")
+          pane.getActiveItem().save = jasmine.createSpy("save")
           pane.saveActiveItem()
-          expect(pane.activeItem.save).toHaveBeenCalled()
+          expect(pane.getActiveItem().save).toHaveBeenCalled()
 
       describe "when the current item has no save method", ->
         it "does nothing", ->
-          expect(pane.activeItem.save).toBeUndefined()
+          expect(pane.getActiveItem().save).toBeUndefined()
           pane.saveActiveItem()
 
     describe "when the current item has no uri", ->
       describe "when the current item has a saveAs method", ->
         it "opens a save dialog and saves the current item as the selected path", ->
-          pane.activeItem.saveAs = jasmine.createSpy("saveAs")
+          pane.getActiveItem().saveAs = jasmine.createSpy("saveAs")
           pane.saveActiveItem()
           expect(atom.showSaveDialogSync).toHaveBeenCalled()
-          expect(pane.activeItem.saveAs).toHaveBeenCalledWith('/selected/path')
+          expect(pane.getActiveItem().saveAs).toHaveBeenCalledWith('/selected/path')
 
       describe "when the current item has no saveAs method", ->
         it "does nothing", ->
-          expect(pane.activeItem.saveAs).toBeUndefined()
+          expect(pane.getActiveItem().saveAs).toBeUndefined()
           pane.saveActiveItem()
           expect(atom.showSaveDialogSync).not.toHaveBeenCalled()
 
@@ -289,22 +365,22 @@ describe "Pane", ->
 
     describe "when the current item has a saveAs method", ->
       it "opens the save dialog and calls saveAs on the item with the selected path", ->
-        pane.activeItem.path = __filename
-        pane.activeItem.saveAs = jasmine.createSpy("saveAs")
+        pane.getActiveItem().path = __filename
+        pane.getActiveItem().saveAs = jasmine.createSpy("saveAs")
         pane.saveActiveItemAs()
         expect(atom.showSaveDialogSync).toHaveBeenCalledWith(__filename)
-        expect(pane.activeItem.saveAs).toHaveBeenCalledWith('/selected/path')
+        expect(pane.getActiveItem().saveAs).toHaveBeenCalledWith('/selected/path')
 
     describe "when the current item does not have a saveAs method", ->
       it "does nothing", ->
-        expect(pane.activeItem.saveAs).toBeUndefined()
+        expect(pane.getActiveItem().saveAs).toBeUndefined()
         pane.saveActiveItemAs()
         expect(atom.showSaveDialogSync).not.toHaveBeenCalled()
 
   describe "::itemForUri(uri)", ->
     it "returns the item for which a call to .getUri() returns the given uri", ->
       pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C"), new Item("D")])
-      [item1, item2, item3] = pane.items
+      [item1, item2, item3] = pane.getItems()
       item1.uri = "a"
       item2.uri = "b"
       expect(pane.itemForUri("a")).toBe item1
@@ -312,24 +388,32 @@ describe "Pane", ->
       expect(pane.itemForUri("bogus")).toBeUndefined()
 
   describe "::moveItem(item, index)", ->
-    it "moves the item to the given index and emits an 'item-moved' event with the item and its new index", ->
-      pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C"), new Item("D")])
-      [item1, item2, item3, item4] = pane.items
-      pane.on 'item-moved', itemMovedHandler = jasmine.createSpy("itemMovedHandler")
+    [pane, item1, item2, item3, item4] = []
 
+    beforeEach ->
+      pane = new Pane(items: [new Item("A"), new Item("B"), new Item("C"), new Item("D")])
+      [item1, item2, item3, item4] = pane.getItems()
+
+    it "moves the item to the given index and invokes ::onDidMoveItem observers", ->
       pane.moveItem(item1, 2)
       expect(pane.getItems()).toEqual [item2, item3, item1, item4]
-      expect(itemMovedHandler).toHaveBeenCalledWith(item1, 2)
-      itemMovedHandler.reset()
 
       pane.moveItem(item2, 3)
       expect(pane.getItems()).toEqual [item3, item1, item4, item2]
-      expect(itemMovedHandler).toHaveBeenCalledWith(item2, 3)
-      itemMovedHandler.reset()
 
       pane.moveItem(item2, 1)
       expect(pane.getItems()).toEqual [item3, item2, item1, item4]
-      expect(itemMovedHandler).toHaveBeenCalledWith(item2, 1)
+
+    it "invokes ::onDidMoveItem() observers", ->
+      events = []
+      pane.onDidMoveItem (event) -> events.push(event)
+
+      pane.moveItem(item1, 2)
+      pane.moveItem(item2, 3)
+      expect(events).toEqual [
+        {item: item1, oldIndex: 0, newIndex: 2}
+        {item: item2, oldIndex: 0, newIndex: 3}
+      ]
 
   describe "::moveItemToPane(item, pane, index)", ->
     [container, pane1, pane2] = []
@@ -339,13 +423,20 @@ describe "Pane", ->
       pane1 = new Pane(items: [new Item("A"), new Item("B"), new Item("C")])
       container = new PaneContainer(root: pane1)
       pane2 = pane1.splitRight(items: [new Item("D"), new Item("E")])
-      [item1, item2, item3] = pane1.items
-      [item4, item5] = pane2.items
+      [item1, item2, item3] = pane1.getItems()
+      [item4, item5] = pane2.getItems()
 
     it "moves the item to the given pane at the given index", ->
       pane1.moveItemToPane(item2, pane2, 1)
-      expect(pane1.items).toEqual [item1, item3]
-      expect(pane2.items).toEqual [item4, item2, item5]
+      expect(pane1.getItems()).toEqual [item1, item3]
+      expect(pane2.getItems()).toEqual [item4, item2, item5]
+
+    it "invokes ::onDidRemoveItem() observers", ->
+      events = []
+      pane1.onDidRemoveItem (event) -> events.push(event)
+      pane1.moveItemToPane(item2, pane2, 1)
+
+      expect(events).toEqual [{item: item2, index: 1, destroyed: false}]
 
     describe "when the moved item the last item in the source pane", ->
       beforeEach ->
@@ -455,7 +546,7 @@ describe "Pane", ->
       pane2 = pane1.splitRight()
 
     it "destroys the pane's destroyable items", ->
-      [item1, item2] = pane1.items
+      [item1, item2] = pane1.getItems()
       pane1.destroy()
       expect(item1.isDestroyed()).toBe true
       expect(item2.isDestroyed()).toBe true
@@ -493,12 +584,12 @@ describe "Pane", ->
 
     it "can serialize and deserialize the pane and all its items", ->
       newPane = pane.testSerialization()
-      expect(newPane.items).toEqual pane.items
+      expect(newPane.getItems()).toEqual pane.getItems()
 
     it "restores the active item on deserialization", ->
       pane.activateItemAtIndex(1)
       newPane = pane.testSerialization()
-      expect(newPane.activeItem).toEqual newPane.items[1]
+      expect(newPane.getActiveItem()).toEqual newPane.itemAtIndex(1)
 
     it "does not include items that cannot be deserialized", ->
       spyOn(console, 'warn')
@@ -506,8 +597,8 @@ describe "Pane", ->
       pane.activateItem(unserializable)
 
       newPane = pane.testSerialization()
-      expect(newPane.activeItem).toEqual pane.items[0]
-      expect(newPane.items.length).toBe pane.items.length - 1
+      expect(newPane.getActiveItem()).toEqual pane.itemAtIndex(0)
+      expect(newPane.getItems().length).toBe pane.getItems().length - 1
 
     it "includes the pane's focus state in the serialized state", ->
       pane.focus()
diff --git a/spec/pane-view-spec.coffee b/spec/pane-view-spec.coffee
index 9f73884b5..4862e639b 100644
--- a/spec/pane-view-spec.coffee
+++ b/spec/pane-view-spec.coffee
@@ -37,7 +37,7 @@ describe "PaneView", ->
 
   describe "when the active pane item changes", ->
     it "hides all item views except the active one", ->
-      expect(pane.activeItem).toBe view1
+      expect(pane.getActiveItem()).toBe view1
       expect(view1.css('display')).not.toBe 'none'
 
       pane.activateItem(view2)
@@ -48,7 +48,7 @@ describe "PaneView", ->
       itemChangedHandler = jasmine.createSpy("itemChangedHandler")
       container.on 'pane:active-item-changed', itemChangedHandler
 
-      expect(pane.activeItem).toBe view1
+      expect(pane.getActiveItem()).toBe view1
       paneModel.activateItem(view2)
       paneModel.activateItem(view2)
 
@@ -149,7 +149,7 @@ describe "PaneView", ->
       activeItemTitleChangedHandler = jasmine.createSpy("activeItemTitleChangedHandler")
       pane.on 'pane:active-item-title-changed', activeItemTitleChangedHandler
 
-      expect(pane.activeItem).toBe view1
+      expect(pane.getActiveItem()).toBe view1
 
       view2.trigger 'title-changed'
       expect(activeItemTitleChangedHandler).not.toHaveBeenCalled()
@@ -246,7 +246,7 @@ describe "PaneView", ->
 
     it "transfers focus to the active view", ->
       focusHandler = jasmine.createSpy("focusHandler")
-      pane.activeItem.on 'focus', focusHandler
+      pane.getActiveItem().on 'focus', focusHandler
       pane.focus()
       expect(focusHandler).toHaveBeenCalled()
 
diff --git a/spec/workspace-spec.coffee b/spec/workspace-spec.coffee
index a75896582..88bcdf49c 100644
--- a/spec/workspace-spec.coffee
+++ b/spec/workspace-spec.coffee
@@ -8,8 +8,12 @@ describe "Workspace", ->
     atom.workspace = workspace = new Workspace
 
   describe "::open(uri, options)", ->
+    openEvents = null
+
     beforeEach ->
-      spyOn(workspace.activePane, 'activate').andCallThrough()
+      openEvents = []
+      workspace.onDidOpen (event) -> openEvents.push(event)
+      spyOn(workspace.getActivePane(), 'activate').andCallThrough()
 
     describe "when the 'searchAllPanes' option is false (default)", ->
       describe "when called without a uri", ->
@@ -21,18 +25,21 @@ describe "Workspace", ->
 
           runs ->
             expect(editor1.getPath()).toBeUndefined()
-            expect(workspace.activePane.items).toEqual [editor1]
-            expect(workspace.activePaneItem).toBe editor1
-            expect(workspace.activePane.activate).toHaveBeenCalled()
+            expect(workspace.getActivePane().items).toEqual [editor1]
+            expect(workspace.getActivePaneItem()).toBe editor1
+            expect(workspace.getActivePane().activate).toHaveBeenCalled()
+            expect(openEvents).toEqual [{uri: undefined, pane: workspace.getActivePane(), item: editor1, index: 0}]
+            openEvents = []
 
           waitsForPromise ->
             workspace.open().then (editor) -> editor2 = editor
 
           runs ->
             expect(editor2.getPath()).toBeUndefined()
-            expect(workspace.activePane.items).toEqual [editor1, editor2]
-            expect(workspace.activePaneItem).toBe editor2
-            expect(workspace.activePane.activate).toHaveBeenCalled()
+            expect(workspace.getActivePane().items).toEqual [editor1, editor2]
+            expect(workspace.getActivePaneItem()).toBe editor2
+            expect(workspace.getActivePane().activate).toHaveBeenCalled()
+            expect(openEvents).toEqual [{uri: undefined, pane: workspace.getActivePane(), item: editor2, index: 1}]
 
       describe "when called with a uri", ->
         describe "when the active pane already has an editor for the given uri", ->
@@ -51,8 +58,29 @@ describe "Workspace", ->
 
             runs ->
               expect(editor).toBe editor1
-              expect(workspace.activePaneItem).toBe editor
-              expect(workspace.activePane.activate).toHaveBeenCalled()
+              expect(workspace.getActivePaneItem()).toBe editor
+              expect(workspace.getActivePane().activate).toHaveBeenCalled()
+
+              expect(openEvents).toEqual [
+                {
+                  uri: atom.project.resolve('a')
+                  item: editor1
+                  pane: atom.workspace.getActivePane()
+                  index: 0
+                }
+                {
+                  uri: atom.project.resolve('b')
+                  item: editor2
+                  pane: atom.workspace.getActivePane()
+                  index: 1
+                }
+                {
+                  uri: atom.project.resolve('a')
+                  item: editor1
+                  pane: atom.workspace.getActivePane()
+                  index: 0
+                }
+              ]
 
         describe "when the active pane does not have an editor for the given uri", ->
           it "adds and activates a new editor for the given path on the active pane", ->
@@ -62,9 +90,9 @@ describe "Workspace", ->
 
             runs ->
               expect(editor.getUri()).toBe atom.project.resolve('a')
-              expect(workspace.activePaneItem).toBe editor
-              expect(workspace.activePane.items).toEqual [editor]
-              expect(workspace.activePane.activate).toHaveBeenCalled()
+              expect(workspace.getActivePaneItem()).toBe editor
+              expect(workspace.getActivePane().items).toEqual [editor]
+              expect(workspace.getActivePane().activate).toHaveBeenCalled()
 
     describe "when the 'searchAllPanes' option is true", ->
       describe "when an editor for the given uri is already open on an inactive pane", ->
@@ -83,14 +111,14 @@ describe "Workspace", ->
             workspace.open('b').then (o) -> editor2 = o
 
           runs ->
-            expect(workspace.activePaneItem).toBe editor2
+            expect(workspace.getActivePaneItem()).toBe editor2
 
           waitsForPromise ->
             workspace.open('a', searchAllPanes: true)
 
           runs ->
-            expect(workspace.activePane).toBe pane1
-            expect(workspace.activePaneItem).toBe editor1
+            expect(workspace.getActivePane()).toBe pane1
+            expect(workspace.getActivePaneItem()).toBe editor1
 
       describe "when no editor for the given uri is open in any pane", ->
         it "opens an editor for the given uri in the active pane", ->
@@ -99,21 +127,21 @@ describe "Workspace", ->
             workspace.open('a', searchAllPanes: true).then (o) -> editor = o
 
           runs ->
-            expect(workspace.activePaneItem).toBe editor
+            expect(workspace.getActivePaneItem()).toBe editor
 
     describe "when the 'split' option is set", ->
       describe "when the 'split' option is 'left'", ->
         it "opens the editor in the leftmost pane of the current pane axis", ->
-          pane1 = workspace.activePane
+          pane1 = workspace.getActivePane()
           pane2 = pane1.splitRight()
-          expect(workspace.activePane).toBe pane2
+          expect(workspace.getActivePane()).toBe pane2
 
           editor = null
           waitsForPromise ->
             workspace.open('a', split: 'left').then (o) -> editor = o
 
           runs ->
-            expect(workspace.activePane).toBe pane1
+            expect(workspace.getActivePane()).toBe pane1
             expect(pane1.items).toEqual [editor]
             expect(pane2.items).toEqual []
 
@@ -123,37 +151,37 @@ describe "Workspace", ->
             workspace.open('a', split: 'left').then (o) -> editor = o
 
           runs ->
-            expect(workspace.activePane).toBe pane1
+            expect(workspace.getActivePane()).toBe pane1
             expect(pane1.items).toEqual [editor]
             expect(pane2.items).toEqual []
 
       describe "when a pane axis is the leftmost sibling of the current pane", ->
         it "opens the new item in the current pane", ->
           editor = null
-          pane1 = workspace.activePane
+          pane1 = workspace.getActivePane()
           pane2 = pane1.splitLeft()
           pane3 = pane2.splitDown()
           pane1.activate()
-          expect(workspace.activePane).toBe pane1
+          expect(workspace.getActivePane()).toBe pane1
 
           waitsForPromise ->
             workspace.open('a', split: 'left').then (o) -> editor = o
 
           runs ->
-            expect(workspace.activePane).toBe pane1
+            expect(workspace.getActivePane()).toBe pane1
             expect(pane1.items).toEqual [editor]
 
       describe "when the 'split' option is 'right'", ->
         it "opens the editor in the rightmost pane of the current pane axis", ->
           editor = null
-          pane1 = workspace.activePane
+          pane1 = workspace.getActivePane()
           pane2 = null
           waitsForPromise ->
             workspace.open('a', split: 'right').then (o) -> editor = o
 
           runs ->
             pane2 = workspace.getPanes().filter((p) -> p != pane1)[0]
-            expect(workspace.activePane).toBe pane2
+            expect(workspace.getActivePane()).toBe pane2
             expect(pane1.items).toEqual []
             expect(pane2.items).toEqual [editor]
 
@@ -163,18 +191,18 @@ describe "Workspace", ->
             workspace.open('a', split: 'right').then (o) -> editor = o
 
           runs ->
-            expect(workspace.activePane).toBe pane2
+            expect(workspace.getActivePane()).toBe pane2
             expect(pane1.items).toEqual []
             expect(pane2.items).toEqual [editor]
 
         describe "when a pane axis is the rightmost sibling of the current pane", ->
           it "opens the new item in a new pane split to the right of the current pane", ->
             editor = null
-            pane1 = workspace.activePane
+            pane1 = workspace.getActivePane()
             pane2 = pane1.splitRight()
             pane3 = pane2.splitDown()
             pane1.activate()
-            expect(workspace.activePane).toBe pane1
+            expect(workspace.getActivePane()).toBe pane1
             pane4 = null
 
             waitsForPromise ->
@@ -182,7 +210,7 @@ describe "Workspace", ->
 
             runs ->
               pane4 = workspace.getPanes().filter((p) -> p != pane1)[0]
-              expect(workspace.activePane).toBe pane4
+              expect(workspace.getActivePane()).toBe pane4
               expect(pane4.items).toEqual [editor]
               expect(workspace.paneContainer.root.children[0]).toBe pane1
               expect(workspace.paneContainer.root.children[1]).toBe pane4
@@ -203,21 +231,21 @@ describe "Workspace", ->
           workspace.open("bar://baz").then (item) ->
             expect(item).toEqual { bar: "bar://baz" }
 
-    it "emits an 'editor-created' event", ->
+    it "notifies ::onDidAddTextEditor observers", ->
       absolutePath = require.resolve('./fixtures/dir/a')
       newEditorHandler = jasmine.createSpy('newEditorHandler')
-      workspace.on 'editor-created', newEditorHandler
+      workspace.onDidAddTextEditor newEditorHandler
 
       editor = null
       waitsForPromise ->
         workspace.open(absolutePath).then (e) -> editor = e
 
       runs ->
-        expect(newEditorHandler).toHaveBeenCalledWith editor
+        expect(newEditorHandler.argsForCall[0][0].textEditor).toBe editor
 
   describe "::reopenItem()", ->
     it "opens the uri associated with the last closed pane that isn't currently open", ->
-      pane = workspace.activePane
+      pane = workspace.getActivePane()
       waitsForPromise ->
         workspace.open('a').then ->
           workspace.open('b').then ->
@@ -226,44 +254,44 @@ describe "Workspace", ->
 
       runs ->
         # does not reopen items with no uri
-        expect(workspace.activePaneItem.getUri()).toBeUndefined()
+        expect(workspace.getActivePaneItem().getUri()).toBeUndefined()
         pane.destroyActiveItem()
 
       waitsForPromise ->
         workspace.reopenItem()
 
       runs ->
-        expect(workspace.activePaneItem.getUri()).not.toBeUndefined()
+        expect(workspace.getActivePaneItem().getUri()).not.toBeUndefined()
 
         # destroy all items
-        expect(workspace.activePaneItem.getUri()).toBe atom.project.resolve('file1')
+        expect(workspace.getActivePaneItem().getUri()).toBe atom.project.resolve('file1')
         pane.destroyActiveItem()
-        expect(workspace.activePaneItem.getUri()).toBe atom.project.resolve('b')
+        expect(workspace.getActivePaneItem().getUri()).toBe atom.project.resolve('b')
         pane.destroyActiveItem()
-        expect(workspace.activePaneItem.getUri()).toBe atom.project.resolve('a')
+        expect(workspace.getActivePaneItem().getUri()).toBe atom.project.resolve('a')
         pane.destroyActiveItem()
 
         # reopens items with uris
-        expect(workspace.activePaneItem).toBeUndefined()
+        expect(workspace.getActivePaneItem()).toBeUndefined()
 
       waitsForPromise ->
         workspace.reopenItem()
 
       runs ->
-        expect(workspace.activePaneItem.getUri()).toBe atom.project.resolve('a')
+        expect(workspace.getActivePaneItem().getUri()).toBe atom.project.resolve('a')
 
       # does not reopen items that are already open
       waitsForPromise ->
         workspace.open('b')
 
       runs ->
-        expect(workspace.activePaneItem.getUri()).toBe atom.project.resolve('b')
+        expect(workspace.getActivePaneItem().getUri()).toBe atom.project.resolve('b')
 
       waitsForPromise ->
         workspace.reopenItem()
 
       runs ->
-        expect(workspace.activePaneItem.getUri()).toBe atom.project.resolve('file1')
+        expect(workspace.getActivePaneItem().getUri()).toBe atom.project.resolve('file1')
 
   describe "::increase/decreaseFontSize()", ->
     it "increases/decreases the font size without going below 1", ->
@@ -282,7 +310,22 @@ describe "Workspace", ->
   describe "::openLicense()", ->
     it "opens the license as plain-text in a buffer", ->
       waitsForPromise -> workspace.openLicense()
-      runs -> expect(workspace.activePaneItem.getText()).toMatch /Copyright/
+      runs -> expect(workspace.getActivePaneItem().getText()).toMatch /Copyright/
+
+  describe "::observeTextEditors()", ->
+    it "invokes the observer with current and future text editors", ->
+      observed = []
+
+      waitsForPromise -> workspace.open()
+      waitsForPromise -> workspace.open()
+      waitsForPromise -> workspace.openLicense()
+
+      runs ->
+        workspace.observeTextEditors (editor) -> observed.push(editor)
+
+      waitsForPromise -> workspace.open()
+
+      expect(observed).toEqual workspace.getTextEditors()
 
   describe "when an editor is destroyed", ->
     it "removes the editor", ->
@@ -292,23 +335,9 @@ describe "Workspace", ->
         workspace.open("a").then (e) -> editor = e
 
       runs ->
-        expect(workspace.getEditors()).toHaveLength 1
+        expect(workspace.getTextEditors()).toHaveLength 1
         editor.destroy()
-        expect(workspace.getEditors()).toHaveLength 0
-
-  describe "when an editor is copied", ->
-    it "emits an 'editor-created' event", ->
-      editor = null
-      handler = jasmine.createSpy('editorCreatedHandler')
-      workspace.on 'editor-created', handler
-
-      waitsForPromise ->
-        workspace.open("a").then (o) -> editor = o
-
-      runs ->
-        expect(handler.callCount).toBe 1
-        editorCopy = editor.copy()
-        expect(handler.callCount).toBe 2
+        expect(workspace.getTextEditors()).toHaveLength 0
 
   it "stores the active grammars used by all the open editors", ->
     waitsForPromise ->
diff --git a/src/pane-axis-view.coffee b/src/pane-axis-view.coffee
index 3039600c0..0018ee6b1 100644
--- a/src/pane-axis-view.coffee
+++ b/src/pane-axis-view.coffee
@@ -1,11 +1,17 @@
+{CompositeDisposable} = require 'event-kit'
 {View} = require './space-pen-extensions'
 PaneView = null
 
 module.exports =
 class PaneAxisView extends View
   initialize: (@model) ->
-    @onChildAdded(child) for child in @model.children
-    @subscribe @model.children, 'changed', @onChildrenChanged
+    @subscriptions = new CompositeDisposable
+
+    @onChildAdded({child, index}) for child, index in @model.getChildren()
+
+    @subscriptions.add @model.onDidAddChild(@onChildAdded)
+    @subscriptions.add @model.onDidRemoveChild(@onChildRemoved)
+    @subscriptions.add @model.onDidReplaceChild(@onChildReplaced)
 
   afterAttach: ->
     @container = @closest('.panes').view()
@@ -14,19 +20,22 @@ class PaneAxisView extends View
     viewClass = model.getViewClass()
     model._view ?= new viewClass(model)
 
-  onChildrenChanged:  ({index, removedValues, insertedValues}) =>
+  onChildReplaced:  ({index, oldChild, newChild}) =>
     focusedElement = document.activeElement if @hasFocus()
-    @onChildRemoved(child, index) for child in removedValues
-    @onChildAdded(child, index + i) for child, i in insertedValues
+    @onChildRemoved({child: oldChild, index})
+    @onChildAdded({child: newChild, index})
     focusedElement?.focus() if document.activeElement is document.body
 
-  onChildAdded: (child, index) =>
+  onChildAdded: ({child, index}) =>
     view = @viewForModel(child)
     @insertAt(index, view)
 
-  onChildRemoved: (child) =>
+  onChildRemoved: ({child}) =>
     view = @viewForModel(child)
     view.detach()
     PaneView ?= require './pane-view'
     if view instanceof PaneView and view.model.isDestroyed()
       @container?.trigger 'pane:removed', [view]
+
+  beforeRemove: ->
+    @subscriptions.dispose()
diff --git a/src/pane-axis.coffee b/src/pane-axis.coffee
index 39657fcf7..9ef95bc8c 100644
--- a/src/pane-axis.coffee
+++ b/src/pane-axis.coffee
@@ -1,4 +1,5 @@
-{Model, Sequence} = require 'theorist'
+{Model} = require 'theorist'
+{Emitter, CompositeDisposable} = require 'event-kit'
 {flatten} = require 'underscore-plus'
 Serializable = require 'serializable'
 
@@ -10,18 +11,17 @@ class PaneAxis extends Model
   atom.deserializers.add(this)
   Serializable.includeInto(this)
 
+  parent: null
+  container: null
+  orientation: null
+
   constructor: ({@container, @orientation, children}) ->
-    @children = Sequence.fromArray(children ? [])
-
-    @subscribe @children.onEach (child) =>
-      child.parent = this
-      child.container = @container
-      @subscribe child, 'destroyed', => @removeChild(child)
-
-    @subscribe @children.onRemoval (child) => @unsubscribe(child)
-
-    @when @children.$length.becomesLessThan(2), 'reparentLastChild'
-    @when @children.$length.becomesLessThan(1), 'destroy'
+    @emitter = new Emitter
+    @subscriptionsByChild = new WeakMap
+    @subscriptions = new CompositeDisposable
+    @children = []
+    if children?
+      @addChild(child) for child in children
 
   deserializeParams: (params) ->
     {container} = params
@@ -32,35 +32,93 @@ class PaneAxis extends Model
     children: @children.map (child) -> child.serialize()
     orientation: @orientation
 
+  getParent: -> @parent
+
+  setParent: (@parent) -> @parent
+
+  getContainer: -> @container
+
+  setContainer: (@container) -> @container
+
   getViewClass: ->
     if @orientation is 'vertical'
       PaneColumnView ?= require './pane-column-view'
     else
       PaneRowView ?= require './pane-row-view'
 
+  getChildren: -> @children.slice()
+
   getPanes: ->
     flatten(@children.map (child) -> child.getPanes())
 
-  addChild: (child, index=@children.length) ->
-    @children.splice(index, 0, child)
+  getItems: ->
+    flatten(@children.map (child) -> child.getItems())
 
-  removeChild: (child) ->
+  onDidAddChild: (fn) ->
+    @emitter.on 'did-add-child', fn
+
+  onDidRemoveChild: (fn) ->
+    @emitter.on 'did-remove-child', fn
+
+  onDidReplaceChild: (fn) ->
+    @emitter.on 'did-replace-child', fn
+
+  onDidDestroy: (fn) ->
+    @emitter.on 'did-destroy', fn
+
+  addChild: (child, index=@children.length) ->
+    child.setParent(this)
+    child.setContainer(@container)
+
+    @subscribeToChild(child)
+
+    @children.splice(index, 0, child)
+    @emitter.emit 'did-add-child', {child, index}
+
+  removeChild: (child, replacing=false) ->
     index = @children.indexOf(child)
     throw new Error("Removing non-existent child") if index is -1
+
+    @unsubscribeFromChild(child)
+
     @children.splice(index, 1)
+    @emitter.emit 'did-remove-child', {child, index}
+    @reparentLastChild() if not replacing and @children.length < 2
 
   replaceChild: (oldChild, newChild) ->
+    @unsubscribeFromChild(oldChild)
+    @subscribeToChild(newChild)
+
+    newChild.setParent(this)
+    newChild.setContainer(@container)
+
     index = @children.indexOf(oldChild)
-    throw new Error("Replacing non-existent child") if index is -1
     @children.splice(index, 1, newChild)
+    @emitter.emit 'did-replace-child', {oldChild, newChild, index}
 
   insertChildBefore: (currentChild, newChild) ->
     index = @children.indexOf(currentChild)
-    @children.splice(index, 0, newChild)
+    @addChild(newChild, index)
 
   insertChildAfter: (currentChild, newChild) ->
     index = @children.indexOf(currentChild)
-    @children.splice(index + 1, 0, newChild)
+    @addChild(newChild, index + 1)
 
   reparentLastChild: ->
     @parent.replaceChild(this, @children[0])
+    @destroy()
+
+  subscribeToChild: (child) ->
+    subscription = child.onDidDestroy => @removeChild(child)
+    @subscriptionsByChild.set(child, subscription)
+    @subscriptions.add(subscription)
+
+  unsubscribeFromChild: (child) ->
+    subscription = @subscriptionsByChild.get(child)
+    @subscriptions.remove(subscription)
+    subscription.dispose()
+
+  destroyed: ->
+    @subscriptions.dispose()
+    @emitter.emit 'did-destroy'
+    @emitter.dispose()
diff --git a/src/pane-container-view.coffee b/src/pane-container-view.coffee
index 77be49420..09a890d74 100644
--- a/src/pane-container-view.coffee
+++ b/src/pane-container-view.coffee
@@ -1,5 +1,6 @@
 {deprecate} = require 'grim'
 Delegator = require 'delegato'
+{CompositeDisposable} = require 'event-kit'
 {$, View} = require './space-pen-extensions'
 PaneView = require './pane-view'
 PaneContainer = require './pane-container'
@@ -15,13 +16,15 @@ class PaneContainerView extends View
     @div class: 'panes'
 
   initialize: (params) ->
+    @subscriptions = new CompositeDisposable
+
     if params instanceof PaneContainer
       @model = params
     else
       @model = new PaneContainer({root: params?.root?.model})
 
-    @subscribe @model.$root, @onRootChanged
-    @subscribe @model.$activePaneItem.changes, @onActivePaneItemChanged
+    @subscriptions.add @model.observeRoot(@onRootChanged)
+    @subscriptions.add @model.onDidChangeActivePaneItem(@onActivePaneItemChanged)
 
   viewForModel: (model) ->
     if model?
@@ -88,7 +91,7 @@ class PaneContainerView extends View
     @viewForModel(@model.activePane)
 
   getActivePaneItem: ->
-    @model.activePaneItem
+    @model.getActivePaneItem()
 
   getActiveView: ->
     @getActivePaneView()?.activeView
@@ -153,3 +156,6 @@ class PaneContainerView extends View
   getPanes: ->
     deprecate("Use PaneContainerView::getPaneViews() instead")
     @getPaneViews()
+
+  beforeRemove: ->
+    @subscriptions.dispose()
diff --git a/src/pane-container.coffee b/src/pane-container.coffee
index 07083263a..14eeae077 100644
--- a/src/pane-container.coffee
+++ b/src/pane-container.coffee
@@ -1,5 +1,6 @@
-{find} = require 'underscore-plus'
+{find, flatten} = require 'underscore-plus'
 {Model} = require 'theorist'
+{Emitter, CompositeDisposable} = require 'event-kit'
 Serializable = require 'serializable'
 Pane = require './pane'
 
@@ -11,10 +12,9 @@ class PaneContainer extends Model
   @version: 1
 
   @properties
-    root: -> new Pane
     activePane: null
 
-  previousRoot: null
+  root: null
 
   @behavior 'activePaneItem', ->
     @$activePane
@@ -23,9 +23,16 @@ class PaneContainer extends Model
 
   constructor: (params) ->
     super
-    @subscribe @$root, @onRootChanged
+
+    @emitter = new Emitter
+    @subscriptions = new CompositeDisposable
+
+    @setRoot(params?.root ? new Pane)
     @destroyEmptyPanes() if params?.destroyEmptyPanes
 
+    @monitorActivePaneItem()
+    @monitorPaneItems()
+
   deserializeParams: (params) ->
     params.root = atom.deserializers.deserialize(params.root, container: this)
     params.destroyEmptyPanes = atom.config.get('core.destroyEmptyPanes')
@@ -36,16 +43,75 @@ class PaneContainer extends Model
     root: @root?.serialize()
     activePaneId: @activePane.id
 
+  onDidChangeRoot: (fn) ->
+    @emitter.on 'did-change-root', fn
+
+  observeRoot: (fn) ->
+    fn(@getRoot())
+    @onDidChangeRoot(fn)
+
+  onDidAddPane: (fn) ->
+    @emitter.on 'did-add-pane', fn
+
+  observePanes: (fn) ->
+    fn(pane) for pane in @getPanes()
+    @onDidAddPane ({pane}) -> fn(pane)
+
+  onDidChangeActivePane: (fn) ->
+    @emitter.on 'did-change-active-pane', fn
+
+  observeActivePane: (fn) ->
+    fn(@getActivePane())
+    @onDidChangeActivePane(fn)
+
+  onDidAddPaneItem: (fn) ->
+    @emitter.on 'did-add-pane-item', fn
+
+  observePaneItems: (fn) ->
+    fn(item) for item in @getPaneItems()
+    @onDidAddPaneItem ({item}) -> fn(item)
+
+  onDidChangeActivePaneItem: (fn) ->
+    @emitter.on 'did-change-active-pane-item', fn
+
+  observeActivePaneItem: (fn) ->
+    fn(@getActivePaneItem())
+    @onDidChangeActivePaneItem(fn)
+
+  onDidDestroyPaneItem: (fn) ->
+    @emitter.on 'did-destroy-pane-item', fn
+
+  getRoot: -> @root
+
+  setRoot: (@root) ->
+    @root.setParent(this)
+    @root.setContainer(this)
+    @emitter.emit 'did-change-root', @root
+    if not @getActivePane()? and @root instanceof Pane
+      @setActivePane(@root)
+
   replaceChild: (oldChild, newChild) ->
     throw new Error("Replacing non-existent child") if oldChild isnt @root
-    @root = newChild
+    @setRoot(newChild)
 
   getPanes: ->
-    @root?.getPanes() ? []
+    @getRoot().getPanes()
+
+  getPaneItems: ->
+    @getRoot().getItems()
 
   getActivePane: ->
     @activePane
 
+  setActivePane: (activePane) ->
+    if activePane isnt @activePane
+      @activePane = activePane
+      @emitter.emit 'did-change-active-pane', @activePane
+    @activePane
+
+  getActivePaneItem: ->
+    @getActivePane().getActiveItem()
+
   paneForUri: (uri) ->
     find @getPanes(), (pane) -> pane.itemForUri(uri)?
 
@@ -73,26 +139,37 @@ class PaneContainer extends Model
     else
       false
 
-  onRootChanged: (root) =>
-    @unsubscribe(@previousRoot) if @previousRoot?
-    @previousRoot = root
-
-    unless root?
-      @activePane = null
-      return
-
-    root.parent = this
-    root.container = this
-
-
-    @activePane ?= root if root instanceof Pane
-
   destroyEmptyPanes: ->
     pane.destroy() for pane in @getPanes() when pane.items.length is 0
 
-  itemDestroyed: (item) ->
-    @emit 'item-destroyed', item
+  paneItemDestroyed: (item) ->
+    @emitter.emit 'did-destroy-pane-item', item
+
+  didAddPane: (pane) ->
+    @emitter.emit 'did-add-pane', pane
 
   # Called by Model superclass when destroyed
   destroyed: ->
     pane.destroy() for pane in @getPanes()
+    @subscriptions.dispose()
+    @emitter.dispose()
+
+  monitorActivePaneItem: ->
+    childSubscription = null
+    @subscriptions.add @observeActivePane (activePane) =>
+      if childSubscription?
+        @subscriptions.remove(childSubscription)
+        childSubscription.dispose()
+
+      childSubscription = activePane.observeActiveItem (activeItem) =>
+        @emitter.emit 'did-change-active-pane-item', activeItem
+
+      @subscriptions.add(childSubscription)
+
+  monitorPaneItems: ->
+    @subscriptions.add @observePanes (pane) =>
+      for item, index in pane.getItems()
+        @emitter.emit 'did-add-pane-item', {item, pane, index}
+
+      pane.onDidAddItem ({item, index}) =>
+        @emitter.emit 'did-add-pane-item', {item, pane, index}
diff --git a/src/pane-view.coffee b/src/pane-view.coffee
index 0d641582e..ac79faaba 100644
--- a/src/pane-view.coffee
+++ b/src/pane-view.coffee
@@ -1,6 +1,7 @@
 {$, View} = require './space-pen-extensions'
 Delegator = require 'delegato'
 {deprecate} = require 'grim'
+{CompositeDisposable} = require 'event-kit'
 PropertyAccessors = require 'property-accessors'
 
 Pane = require './pane'
@@ -33,6 +34,8 @@ class PaneView extends View
   previousActiveItem: null
 
   initialize: (args...) ->
+    @subscriptions = new CompositeDisposable
+
     if args[0] instanceof Pane
       @model = args[0]
     else
@@ -44,13 +47,13 @@ class PaneView extends View
     @handleEvents()
 
   handleEvents: ->
-    @subscribe @model.$activeItem, @onActiveItemChanged
-    @subscribe @model, 'item-added', @onItemAdded
-    @subscribe @model, 'item-removed', @onItemRemoved
-    @subscribe @model, 'item-moved', @onItemMoved
-    @subscribe @model, 'before-item-destroyed', @onBeforeItemDestroyed
-    @subscribe @model, 'activated', @onActivated
-    @subscribe @model.$active, @onActiveStatusChanged
+    @subscriptions.add @model.observeActiveItem(@onActiveItemChanged)
+    @subscriptions.add @model.onDidAddItem(@onItemAdded)
+    @subscriptions.add @model.onDidRemoveItem(@onItemRemoved)
+    @subscriptions.add @model.onDidMoveItem(@onItemMoved)
+    @subscriptions.add @model.onWillDestroyItem(@onBeforeItemDestroyed)
+    @subscriptions.add @model.onDidActivate(@onActivated)
+    @subscriptions.add @model.observeActive(@onActiveStatusChanged)
 
     @subscribe this, 'focusin', => @model.focus()
     @subscribe this, 'focusout', => @model.blur()
@@ -160,10 +163,10 @@ class PaneView extends View
 
     @trigger 'pane:active-item-changed', [item]
 
-  onItemAdded: (item, index) =>
+  onItemAdded: ({item, index}) =>
     @trigger 'pane:item-added', [item, index]
 
-  onItemRemoved: (item, index, destroyed) =>
+  onItemRemoved: ({item, index, destroyed}) =>
     if item instanceof $
       viewToRemove = item
     else if viewToRemove = @viewsByItem.get(item)
@@ -177,7 +180,7 @@ class PaneView extends View
 
     @trigger 'pane:item-removed', [item, index]
 
-  onItemMoved: (item, newIndex) =>
+  onItemMoved: ({item, newIndex}) =>
     @trigger 'pane:item-moved', [item, newIndex]
 
   onBeforeItemDestroyed: (item) =>
@@ -219,6 +222,7 @@ class PaneView extends View
     @closest('.panes').view()
 
   beforeRemove: ->
+    @subscriptions.dispose()
     @model.destroy() unless @model.isDestroyed()
 
   remove: (selector, keepData) ->
diff --git a/src/pane.coffee b/src/pane.coffee
index 678e2156e..d56ae007b 100644
--- a/src/pane.coffee
+++ b/src/pane.coffee
@@ -1,47 +1,16 @@
 {find, compact, extend, last} = require 'underscore-plus'
-{Model, Sequence} = require 'theorist'
+{Model} = require 'theorist'
+{Emitter} = require 'event-kit'
 Serializable = require 'serializable'
+Grim = require 'grim'
 PaneAxis = require './pane-axis'
 Editor = require './editor'
 PaneView = null
 
-# Extended: A container for multiple items, one of which is *active* at a given
-# time. With the default packages, a tab is displayed for each item and the
-# active item's view is displayed.
-#
-# ## Events
-# ### activated
-#
-# Extended: Emit when this pane as been activated
-#
-# ### item-added
-#
-# Extended: Emit when an item was added to the pane
-#
-# * `item` The pane item that has been added
-# * `index` {Number} Index in the pane
-#
-# ### before-item-destroyed
-#
-# Extended: Emit before the item is destroyed
-#
-# * `item` The pane item that will be destoryed
-#
-# ### item-removed
-#
-# Extended: Emit when the item was removed from the pane
-#
-# * `item` The pane item that was removed
-# * `index` {Number} Index in the pane
-# * `destroying` {Boolean} `true` when the item is being removed because of destruction
-#
-# ### item-moved
-#
-# Extended: Emit when an item was moved within the pane
-#
-# * `item` The pane item that was moved
-# * `newIndex` {Number} Index that the item was moved to
-#
+# Extended: A container for presenting content in the center of the workspace.
+# Panes can contain multiple items, one of which is *active* at a given time.
+# The view corresponding to the active item is displayed in the interface. In
+# the default configuration, tabs are also displayed for each item.
 module.exports =
 class Pane extends Model
   atom.deserializers.add(this)
@@ -64,15 +33,11 @@ class Pane extends Model
   constructor: (params) ->
     super
 
-    @items = Sequence.fromArray(compact(params?.items ? []))
-    @activeItem ?= @items[0]
+    @emitter = new Emitter
+    @items = []
 
-    @subscribe @items.onEach (item) =>
-      if typeof item.on is 'function'
-        @subscribe item, 'destroyed', => @removeItem(item, true)
-
-    @subscribe @items.onRemoval (item, index) =>
-      @unsubscribe item if typeof item.on is 'function'
+    @addItems(compact(params?.items ? []))
+    @setActiveItem(@items[0]) unless @getActiveItem()?
 
   # Called by the Serializable mixin during serialization.
   serializeParams: ->
@@ -91,7 +56,174 @@ class Pane extends Model
   # Called by the view layer to construct a view for this model.
   getViewClass: -> PaneView ?= require './pane-view'
 
-  isActive: -> @active
+  getParent: -> @parent
+
+  setParent: (@parent) -> @parent
+
+  getContainer: -> @container
+
+  setContainer: (container) ->
+    container.didAddPane({pane: this}) unless container is @container
+    @container = container
+
+  ###
+  Section: Event Subscription
+  ###
+
+  # Public: Invoke the given callback when the pane is activated.
+  #
+  # The given callback will be invoked whenever {::activate} is called on the
+  # pane, even if it is already active at the time.
+  #
+  # * `callback` {Function} to be called when the pane is activated.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidActivate: (callback) ->
+    @emitter.on 'did-activate', callback
+
+  # Public: Invoke the given callback when the pane is destroyed.
+  #
+  # * `callback` {Function} to be called when the pane is destroyed.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidDestroy: (callback) ->
+    @emitter.on 'did-destroy', callback
+
+  # Public: Invoke the given callback when the value of the {::isActive}
+  # property changes.
+  #
+  # * `callback` {Function} to be called when the value of the {::isActive}
+  #   property changes.
+  #   * `active` {Boolean} indicating whether the pane is active.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidChangeActive: (callback) ->
+    @container.onDidChangeActivePane (activePane) =>
+      callback(this is activePane)
+
+  # Public: Invoke the given callback with the current and future values of the
+  # {::isActive} property.
+  #
+  # * `callback` {Function} to be called with the current and future values of
+  #   the {::isActive} property.
+  #   * `active` {Boolean} indicating whether the pane is active.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  observeActive: (callback) ->
+    callback(@isActive())
+    @onDidChangeActive(callback)
+
+  # Public: Invoke the given callback when an item is added to the pane.
+  #
+  # * `callback` {Function} to be called with when items are added.
+  #   * `event` {Object} with the following keys:
+  #     * `item` The added pane item.
+  #     * `index` {Number} indicating where the item is located.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidAddItem: (callback) ->
+    @emitter.on 'did-add-item', callback
+
+  # Public: Invoke the given callback when an item is removed from the pane.
+  #
+  # * `callback` {Function} to be called with when items are removed.
+  #   * `event` {Object} with the following keys:
+  #     * `item` The removed pane item.
+  #     * `index` {Number} indicating where the item was located.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidRemoveItem: (callback) ->
+    @emitter.on 'did-remove-item', callback
+
+  # Public: Invoke the given callback when an item is moved within the pane.
+  #
+  # * `callback` {Function} to be called with when items are moved.
+  #   * `event` {Object} with the following keys:
+  #     * `item` The removed pane item.
+  #     * `oldIndex` {Number} indicating where the item was located.
+  #     * `newIndex` {Number} indicating where the item is now located.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidMoveItem: (callback) ->
+    @emitter.on 'did-move-item', callback
+
+  # Public: Invoke the given callback with all current and future items.
+  #
+  # * `callback` {Function} to be called with current and future items.
+  #   * `item` An item that is present in {::getItems} at the time of
+  #     subscription or that is added at some later time.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  observeItems: (callback) ->
+    callback(item) for item in @getItems()
+    @onDidAddItem ({item}) -> callback(item)
+
+  # Public: Invoke the given callback when the value of {::getActiveItem}
+  # changes.
+  #
+  # * `callback` {Function} to be called with when the active item changes.
+  #   * `activeItem` The current active item.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidChangeActiveItem: (callback) ->
+    @emitter.on 'did-change-active-item', callback
+
+  # Public: Invoke the given callback with the current and future values of
+  # {::getActiveItem}.
+  #
+  # * `callback` {Function} to be called with the current and future active
+  #   items.
+  #   * `activeItem` The current active item.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  observeActiveItem: (callback) ->
+    callback(@getActiveItem())
+    @onDidChangeActiveItem(callback)
+
+  # Public: Invoke the given callback before items are destroyed.
+  #
+  # * `callback` {Function} to be called before items are destroyed.
+  #   * `event` {Object} with the following keys:
+  #     * `item` The item that will be destroyed.
+  #     * `index` The location of the item.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to
+  # unsubscribe.
+  onWillDestroyItem: (callback) ->
+    @emitter.on 'will-destroy-item', callback
+
+  on: (eventName) ->
+    switch eventName
+      when 'activated'
+        Grim.deprecate("Use Pane::onDidActivate instead")
+      when 'destroyed'
+        Grim.deprecate("Use Pane::onDidDestroy instead")
+      when 'item-added'
+        Grim.deprecate("Use Pane::onDidAddItem instead")
+      when 'item-removed'
+        Grim.deprecate("Use Pane::onDidRemoveItem instead")
+      when 'item-moved'
+        Grim.deprecate("Use Pane::onDidMoveItem instead")
+      when 'before-item-destroyed'
+        Grim.deprecate("Use Pane::onWillDestroyItem instead")
+      else
+        Grim.deprecate("Subscribing via ::on is deprecated. Use documented event subscription methods instead.")
+    super
+
+  behavior: (behaviorName) ->
+    switch behaviorName
+      when 'active'
+        Grim.deprecate("The $active behavior property is deprecated. Use ::observeActive or ::onDidChangeActive instead.")
+      when 'container'
+        Grim.deprecate("The $container behavior property is deprecated.")
+      when 'activeItem'
+        Grim.deprecate("The $activeItem behavior property is deprecated. Use ::observeActiveItem or ::onDidChangeActiveItem instead.")
+      when 'focused'
+        Grim.deprecate("The $focused behavior property is deprecated.")
+      else
+        Grim.deprecate("Pane::behavior is deprecated. Use event subscription methods instead.")
+
+    super
 
   # Called by the view layer to indicate that the pane has gained focus.
   focus: ->
@@ -103,14 +235,12 @@ class Pane extends Model
     @focused = false
     true # if this is called from an event handler, don't cancel it
 
-  # Public: Makes this pane the *active* pane, causing it to gain focus
-  # immediately.
-  activate: ->
-    @container?.activePane = this
-    @emit 'activated'
-
   getPanes: -> [this]
 
+  ###
+  Section: Items
+  ###
+
   # Public: Get the items in this pane.
   #
   # Returns an {Array} of items.
@@ -120,15 +250,23 @@ class Pane extends Model
   # Public: Get the active pane item in this pane.
   #
   # Returns a pane item.
-  getActiveItem: ->
+  getActiveItem: -> @activeItem
+
+  setActiveItem: (activeItem) ->
+    unless activeItem is @activeItem
+      @activeItem = activeItem
+      @emitter.emit 'did-change-active-item', @activeItem
     @activeItem
 
-  # Public: Returns an {Editor} if the pane item is an {Editor}, or null
-  # otherwise.
+  # Return an {Editor} if the pane item is an {Editor}, or null otherwise.
   getActiveEditor: ->
     @activeItem if @activeItem instanceof Editor
 
-  # Public: Returns the item at the specified index.
+  # Public: Return the item at the given index.
+  #
+  # * `index` {Number}
+  #
+  # Returns an item or `null` if no item exists at the given index.
   itemAtIndex: (index) ->
     @items[index]
 
@@ -148,86 +286,115 @@ class Pane extends Model
     else
       @activateItemAtIndex(@items.length - 1)
 
-  # Returns the index of the current active item.
+  # Public: Get the index of the active item.
+  #
+  # Returns a {Number}.
   getActiveItemIndex: ->
     @items.indexOf(@activeItem)
 
-  # Makes the item at the given index active.
+  # Public: Activate the item at the given index.
+  #
+  # * `index` {Number}
   activateItemAtIndex: (index) ->
     @activateItem(@itemAtIndex(index))
 
-  # Makes the given item active, adding the item if necessary.
+  # Public: Make the given item *active*, causing it to be displayed by
+  # the pane's view.
   activateItem: (item) ->
     if item?
       @addItem(item)
-      @activeItem = item
+      @setActiveItem(item)
 
-  # Public: Adds the item to the pane.
+  # Public: Add the given item to the pane.
   #
-  # * `item` The item to add. It can be a model with an associated view or a view.
-  # * `index` (optional) {Number} at which to add the item. If omitted, the item is
-  #   added after the current active item.
+  # * `item` The item to add. It can be a model with an associated view or a
+  #   view.
+  # * `index` (optional) {Number} indicating the index at which to add the item.
+  #   If omitted, the item is added after the current active item.
   #
-  # Returns the added item
+  # Returns the added item.
   addItem: (item, index=@getActiveItemIndex() + 1) ->
     return if item in @items
 
+    if typeof item.on is 'function'
+      @subscribe item, 'destroyed', => @removeItem(item, true)
+
     @items.splice(index, 0, item)
     @emit 'item-added', item, index
-    @activeItem ?= item
+    @emitter.emit 'did-add-item', {item, index}
+    @setActiveItem(item) unless @getActiveItem()?
     item
 
-  # Public: Adds the given items to the pane.
+  # Public: Add the given items to the pane.
   #
-  # * `items` An {Array} of items to add. Items can be models with associated
-  #   views or views. Any items that are already present in items will
-  #   not be added.
-  # * `index` (optional) {Number} index at which to add the item. If omitted, the item is
-  #   added after the current active item.
+  # * `items` An {Array} of items to add. Items can be views or models with
+  #   associated views. Any objects that are already present in the pane's
+  #   current items will not be added again.
+  # * `index` (optional) {Number} index at which to add the items. If omitted,
+  #   the item is #   added after the current active item.
   #
-  # Returns an {Array} of the added items
+  # Returns an {Array} of added items.
   addItems: (items, index=@getActiveItemIndex() + 1) ->
     items = items.filter (item) => not (item in @items)
     @addItem(item, index + i) for item, i in items
     items
 
-  removeItem: (item, destroying) ->
+  removeItem: (item, destroyed=false) ->
     index = @items.indexOf(item)
     return if index is -1
+
+    if typeof item.on is 'function'
+      @unsubscribe item
+
     if item is @activeItem
       if @items.length is 1
-        @activeItem = undefined
+        @setActiveItem(undefined)
       else if index is 0
         @activateNextItem()
       else
         @activatePreviousItem()
     @items.splice(index, 1)
-    @emit 'item-removed', item, index, destroying
-    @container?.itemDestroyed(item) if destroying
+    @emit 'item-removed', item, index, destroyed
+    @emitter.emit 'did-remove-item', {item, index, destroyed}
+    @container?.paneItemDestroyed(item) if destroyed
     @destroy() if @items.length is 0 and atom.config.get('core.destroyEmptyPanes')
 
-  # Public: Moves the given item to the specified index.
+  # Public: Move the given item to the given index.
+  #
+  # * `item` The item to move.
+  # * `index` {Number} indicating the index to which to move the item.
   moveItem: (item, newIndex) ->
     oldIndex = @items.indexOf(item)
     @items.splice(oldIndex, 1)
     @items.splice(newIndex, 0, item)
     @emit 'item-moved', item, newIndex
+    @emitter.emit 'did-move-item', {item, oldIndex, newIndex}
 
-  # Public: Moves the given item to the given index at another pane.
+  # Public: Move the given item to the given index on another pane.
+  #
+  # * `item` The item to move.
+  # * `pane` {Pane} to which to move the item.
+  # * `index` {Number} indicating the index to which to move the item in the
+  #   given pane.
   moveItemToPane: (item, pane, index) ->
     pane.addItem(item, index)
     @removeItem(item)
 
-  # Public: Destroys the currently active item and make the next item active.
+  # Public: Destroy the active item and activate the next item.
   destroyActiveItem: ->
     @destroyItem(@activeItem)
     false
 
-  # Public: Destroys the given item. If it is the active item, activate the next
-  # one. If this is the last item, also destroys the pane.
+  # Public: Destroy the given item.
+  #
+  # If the item is active, the next item will be activated. If the item is the
+  # last item, the pane will be destroyed if the `core.destroyEmptyPanes` config
+  # setting is `true`.
   destroyItem: (item) ->
-    if item?
+    index = @items.indexOf(item)
+    if index isnt -1
       @emit 'before-item-destroyed', item
+      @emitter.emit 'will-destroy-item', {item, index}
       if @promptToSaveItem(item)
         @removeItem(item, true)
         item.destroy?()
@@ -235,27 +402,14 @@ class Pane extends Model
       else
         false
 
-  # Public: Destroys all items and destroys the pane.
+  # Public: Destroy all items.
   destroyItems: ->
     @destroyItem(item) for item in @getItems()
 
-  # Public: Destroys all items but the active one.
+  # Public: Destroy all items except for the active item.
   destroyInactiveItems: ->
     @destroyItem(item) for item in @getItems() when item isnt @activeItem
 
-  destroy: ->
-    if @container?.isAlive() and @container.getPanes().length is 1
-      @destroyItems()
-    else
-      super
-
-  # Called by model superclass.
-  destroyed: ->
-    @container.activateNextPane() if @isActive()
-    item.destroy?() for item in @items.slice()
-
-  # Public: Prompts the user to save the given item if it can be saved and is
-  # currently unsaved.
   promptToSaveItem: (item) ->
     return true unless item.shouldPromptToSave?()
 
@@ -270,18 +424,23 @@ class Pane extends Model
       when 1 then false
       when 2 then true
 
-  # Public: Saves the active item.
-  saveActiveItem: ->
-    @saveItem(@activeItem)
+  # Public: Save the active item.
+  saveActiveItem: (nextAction) ->
+    @saveItem(@getActiveItem(), nextAction)
 
-  # Public: Saves the active item at a prompted-for location.
-  saveActiveItemAs: ->
-    @saveItemAs(@activeItem)
+  # Public: Prompt the user for a location and save the active item with the
+  # path they select.
+  #
+  # * `nextAction` (optional) {Function} which will be called after the item is
+  #   successfully saved.
+  saveActiveItemAs: (nextAction) ->
+    @saveItemAs(@getActiveItem(), nextAction)
 
-  # Public: Saves the specified item.
+  # Public: Save the given item.
   #
   # * `item` The item to save.
-  # * `nextAction` (optional) {Function} which will be called after the item is saved.
+  # * `nextAction` (optional) {Function} which will be called after the item is
+  #   successfully saved.
   saveItem: (item, nextAction) ->
     if item?.getUri?()
       item.save?()
@@ -289,10 +448,12 @@ class Pane extends Model
     else
       @saveItemAs(item, nextAction)
 
-  # Public: Saves the given item at a prompted-for location.
+  # Public: Prompt the user for a location and save the active item with the
+  # path they select.
   #
   # * `item` The item to save.
-  # * `nextAction` (optional) {Function} which will be called after the item is saved.
+  # * `nextAction` (optional) {Function} which will be called after the item is
+  #   successfully saved.
   saveItemAs: (item, nextAction) ->
     return unless item?.saveAs?
 
@@ -302,17 +463,20 @@ class Pane extends Model
       item.saveAs(newItemPath)
       nextAction?()
 
-  # Public: Saves all items.
+  # Public: Save all items.
   saveItems: ->
     @saveItem(item) for item in @getItems()
 
-  # Public: Returns the first item that matches the given URI or undefined if
+  # Public: Return the first item that matches the given URI or undefined if
   # none exists.
+  #
+  # * `uri` {String} containing a URI.
   itemForUri: (uri) ->
     find @items, (item) -> item.getUri?() is uri
 
-  # Public: Activates the first item that matches the given URI. Returns a
-  # boolean indicating whether a matching item was found.
+  # Public: Activate the first item that matches the given URI.
+  #
+  # Returns a {Boolean} indicating whether an item matching the URI was found.
   activateItemForUri: (uri) ->
     if item = @itemForUri(uri)
       @activateItem(item)
@@ -324,19 +488,55 @@ class Pane extends Model
     if @activeItem?
       @activeItem.copy?() ? atom.deserializers.deserialize(@activeItem.serialize())
 
-  # Public: Creates a new pane to the left of the receiver.
+  ###
+  Section: Lifecycle
+  ###
+
+  # Public: Determine whether the pane is active.
   #
-  # * `params` {Object} with keys
-  #   * `items` (optional) {Array} of items with which to construct the new pane.
+  # Returns a {Boolean}.
+  isActive: ->
+    @container?.getActivePane() is this
+
+  # Public: Makes this pane the *active* pane, causing it to gain focus.
+  activate: ->
+    @container?.setActivePane(this)
+    @emit 'activated'
+    @emitter.emit 'did-activate'
+
+  # Public: Close the pane and destroy all its items.
+  #
+  # If this is the last pane, all the items will be destroyed but the pane
+  # itself will not be destroyed.
+  destroy: ->
+    if @container?.isAlive() and @container.getPanes().length is 1
+      @destroyItems()
+    else
+      super
+
+  # Called by model superclass.
+  destroyed: ->
+    @container.activateNextPane() if @isActive()
+    @emitter.emit 'did-destroy'
+    item.destroy?() for item in @items.slice()
+
+  ###
+  Section: Splitting
+  ###
+
+  # Public: Create a new pane to the left of this pane.
+  #
+  # * `params` (optional) {Object} with the following keys:
+  #   * `items` (optional) {Array} of items to add to the new pane.
   #
   # Returns the new {Pane}.
   splitLeft: (params) ->
     @split('horizontal', 'before', params)
 
-  # Public: Creates a new pane to the right of the receiver.
+  # Public: Create a new pane to the right of this pane.
   #
-  # * `params` {Object} with keys:
-  #   * `items` (optional) {Array} of items with which to construct the new pane.
+  # * `params` (optional) {Object} with the following keys:
+  #   * `items` (optional) {Array} of items to add to the new pane.
   #
   # Returns the new {Pane}.
   splitRight: (params) ->
@@ -344,8 +544,8 @@ class Pane extends Model
 
   # Public: Creates a new pane above the receiver.
   #
-  # * `params` {Object} with keys:
-  #   * `items` (optional) {Array} of items with which to construct the new pane.
+  # * `params` (optional) {Object} with the following keys:
+  #   * `items` (optional) {Array} of items to add to the new pane.
   #
   # Returns the new {Pane}.
   splitUp: (params) ->
@@ -353,8 +553,8 @@ class Pane extends Model
 
   # Public: Creates a new pane below the receiver.
   #
-  # * `params` {Object} with keys:
-  #   * `items` (optional) {Array} of items with which to construct the new pane.
+  # * `params` (optional) {Object} with the following keys:
+  #   * `items` (optional) {Array} of items to add to the new pane.
   #
   # Returns the new {Pane}.
   splitDown: (params) ->
diff --git a/src/workspace-view.coffee b/src/workspace-view.coffee
index 9da0d7b90..b4ae47318 100644
--- a/src/workspace-view.coffee
+++ b/src/workspace-view.coffee
@@ -84,7 +84,7 @@ class WorkspaceView extends View
     @panes.replaceWith(panes)
     @panes = panes
 
-    @subscribe @model, 'uri-opened', => @trigger 'uri-opened'
+    @subscribe @model.onDidOpen => @trigger 'uri-opened'
 
     @subscribe scrollbarStyle, (style) =>
       @removeClass('scrollbars-visible-always scrollbars-visible-when-scrolling')
@@ -409,4 +409,4 @@ class WorkspaceView extends View
   # Deprecated: Call {Workspace::getActivePaneItem} instead.
   getActivePaneItem: ->
     deprecate("Use Workspace::getActivePaneItem instead")
-    @model.activePaneItem
+    @model.getActivePaneItem()
diff --git a/src/workspace.coffee b/src/workspace.coffee
index 85870ef1b..97fff29e1 100644
--- a/src/workspace.coffee
+++ b/src/workspace.coffee
@@ -5,6 +5,7 @@ _ = require 'underscore-plus'
 Q = require 'q'
 Serializable = require 'serializable'
 Delegator = require 'delegato'
+{Emitter} = require 'event-kit'
 Editor = require './editor'
 PaneContainer = require './pane-container'
 Pane = require './pane'
@@ -16,17 +17,6 @@ Pane = require './pane'
 # editors, and manipulate panes. To add panels, you'll need to use the
 # {WorkspaceView} class for now until we establish APIs at the model layer.
 #
-# ## Events
-#
-# ### uri-opened
-#
-# Extended: Emit when something has been opened. This can be anything, from an
-# editor to the settings view. You can get the new item via {::getActivePaneItem}
-#
-# ### editor-created
-#
-# Extended: Emit when an editor is created (a file opened).
-#
 # * `editor` {Editor} the new editor
 #
 module.exports =
@@ -44,9 +34,11 @@ class Workspace extends Model
   constructor: ->
     super
 
+    @emitter = new Emitter
     @openers = []
 
-    @subscribe @paneContainer, 'item-destroyed', @onPaneItemDestroyed
+    @paneContainer.onDidDestroyPaneItem(@onPaneItemDestroyed)
+
     @registerOpener (filePath) =>
       switch filePath
         when 'atom://.atom/stylesheet'
@@ -83,34 +75,130 @@ class Workspace extends Model
       for scopeName in includedGrammarScopes ? []
         addGrammar(atom.syntax.grammarForScopeName(scopeName))
 
-    addGrammar(editor.getGrammar()) for editor in @getEditors()
+    addGrammar(editor.getGrammar()) for editor in @getTextEditors()
     _.uniq(packageNames)
 
   editorAdded: (editor) ->
     @emit 'editor-created', editor
 
-  # Public: Register a function to be called for every current and future
-  # {Editor} in the workspace.
+  ###
+  Section: Event Subscription
+  ###
+
+  # Extended: Invoke the given callback when a pane is added to the workspace.
   #
-  # * `callback` A {Function} with an {Editor} as its only argument.
+  # * `callback` {Function} to be called panes are added.
+  #   * `event` {Object} with the following keys:
+  #     * `pane` The added pane.
   #
-  # Returns a subscription object with an `.off` method that you can call to
-  # unregister the callback.
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidAddPane: (callback) -> @paneContainer.onDidAddPane(callback)
+
+  # Extended: Invoke the given callback with all current and future panes in the
+  # workspace.
+  #
+  # * `callback` {Function} to be called with current and future panes.
+  #   * `pane` A {Pane} that is present in {::getPanes} at the time of
+  #      subscription or that is added at some later time.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  observePanes: (callback) -> @paneContainer.observePanes(callback)
+
+  # Extended: Invoke the given callback when a pane item is added to the
+  # workspace.
+  #
+  # * `callback` {Function} to be called panes are added.
+  #   * `event` {Object} with the following keys:
+  #     * `item` The added pane item.
+  #     * `pane` {Pane} containing the added item.
+  #     * `index` {Number} indicating the index of the added item in its pane.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidAddPaneItem: (callback) -> @paneContainer.onDidAddPaneItem(callback)
+
+  # Extended: Invoke the given callback with all current and future panes items in
+  # the workspace.
+  #
+  # * `callback` {Function} to be called with current and future pane items.
+  #   * `item` An item that is present in {::getPaneItems} at the time of
+  #      subscription or that is added at some later time.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  observePaneItems: (callback) -> @paneContainer.observePaneItems(callback)
+
+  # Extended: Invoke the given callback when a text editor is added to the
+  # workspace.
+  #
+  # * `callback` {Function} to be called panes are added.
+  #   * `event` {Object} with the following keys:
+  #     * `textEditor` {Editor} that was added.
+  #     * `pane` {Pane} containing the added text editor.
+  #     * `index` {Number} indicating the index of the added text editor in its
+  #        pane.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidAddTextEditor: (callback) ->
+    @onDidAddPaneItem ({item, pane, index}) ->
+      callback({textEditor: item, pane, index}) if item instanceof Editor
+
+  # Essential: Invoke the given callback with all current and future text
+  # editors in the workspace.
+  #
+  # * `callback` {Function} to be called with current and future text editors.
+  #   * `editor` An {Editor} that is present in {::getTextEditors} at the time
+  #     of subscription or that is added at some later time.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  observeTextEditors: (callback) ->
+    callback(textEditor) for textEditor in @getTextEditors()
+    @onDidAddTextEditor ({textEditor}) -> callback(textEditor)
+
+  # Essential: Invoke the given callback whenever an item is opened. Unlike
+  # ::onDidAddPaneItem, observers will be notified for items that are already
+  # present in the workspace when they are reopened.
+  #
+  # * `callback` {Function} to be called whenever an item is opened.
+  #   * `event` {Object} with the following keys:
+  #     * `uri` {String} representing the opened URI. Could be `undefined`.
+  #     * `item` The opened item.
+  #     * `pane` The pane in which the item was opened.
+  #     * `index` The index of the opened item on its pane.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidOpen: (callback) ->
+    @emitter.on 'did-open', callback
+
   eachEditor: (callback) ->
+    deprecate("Use Workspace::observeTextEditors instead")
+
     callback(editor) for editor in @getEditors()
     @subscribe this, 'editor-created', (editor) -> callback(editor)
 
-  # Public: Get all current editors in the workspace.
-  #
-  # Returns an {Array} of {Editor}s.
   getEditors: ->
+    deprecate("Use Workspace::getTextEditors instead")
+
     editors = []
     for pane in @paneContainer.getPanes()
       editors.push(item) for item in pane.getItems() when item instanceof Editor
 
     editors
 
-  # Public: Open a given a URI in Atom asynchronously.
+  on: (eventName) ->
+    switch eventName
+      when 'editor-created'
+        deprecate("Use Workspace::onDidAddTextEditor or Workspace::observeTextEditors instead.")
+      when 'uri-opened'
+        deprecate("Use Workspace::onDidAddPaneItem instead.")
+      else
+        deprecate("Subscribing via ::on is deprecated. Use documented event subscription methods instead.")
+
+    super
+
+  ###
+  Section: Opening
+  ###
+
+  # Essential: Open a given a URI in Atom asynchronously.
   #
   # * `uri` A {String} containing a URI.
   # * `options` (optional) {Object}
@@ -137,11 +225,11 @@ class Workspace extends Model
     pane = @paneContainer.paneForUri(uri) if searchAllPanes
     pane ?= switch split
       when 'left'
-        @activePane.findLeftmostSibling()
+        @getActivePane().findLeftmostSibling()
       when 'right'
-        @activePane.findOrCreateRightmostSibling()
+        @getActivePane().findOrCreateRightmostSibling()
       else
-        @activePane
+        @getActivePane()
 
     @openUriInPane(uri, pane, options)
 
@@ -195,12 +283,14 @@ class Workspace extends Model
         @itemOpened(item)
         pane.activateItem(item)
         pane.activate() if changeFocus
+        index = pane.getActiveItemIndex()
         @emit "uri-opened"
+        @emitter.emit 'did-open', {uri, pane, item, index}
         item
       .catch (error) ->
         console.error(error.stack ? error)
 
-  # Public: Asynchronously reopens the last-closed item's URI if it hasn't already been
+  # Extended: Asynchronously reopens the last-closed item's URI if it hasn't already been
   # reopened.
   #
   # Returns a promise that is resolved when the item is opened
@@ -216,7 +306,7 @@ class Workspace extends Model
     if uri = @destroyedItemUris.pop()
       @openSync(uri)
 
-  # Public: Register an opener for a uri.
+  # Extended: Register an opener for a uri.
   #
   # An {Editor} will be used if no openers return a value.
   #
@@ -232,52 +322,52 @@ class Workspace extends Model
   registerOpener: (opener) ->
     @openers.push(opener)
 
-  # Public: Unregister an opener registered with {::registerOpener}.
+  # Extended: Unregister an opener registered with {::registerOpener}.
   unregisterOpener: (opener) ->
     _.remove(@openers, opener)
 
   getOpeners: ->
     @openers
 
-  # Public: Get the active {Pane}.
+  ###
+  Section: Pane Items
+  ###
+
+  # Essential: Get all pane items in the workspace.
   #
-  # Returns a {Pane}.
-  getActivePane: ->
-    @paneContainer.activePane
+  # Returns an {Array} of items.
+  getPaneItems: ->
+    @paneContainer.getPaneItems()
 
-  # Public: Get all {Pane}s.
-  #
-  # Returns an {Array} of {Pane}s.
-  getPanes: ->
-    @paneContainer.getPanes()
-
-  # Public: Save all pane items.
-  saveAll: ->
-    @paneContainer.saveAll()
-
-  # Public: Make the next pane active.
-  activateNextPane: ->
-    @paneContainer.activateNextPane()
-
-  # Public: Make the previous pane active.
-  activatePreviousPane: ->
-    @paneContainer.activatePreviousPane()
-
-  # Public: Get the first pane {Pane} with an item for the given URI.
-  #
-  # * `uri` {String} uri
-  #
-  # Returns a {Pane} or `undefined` if no pane exists for the given URI.
-  paneForUri: (uri) ->
-    @paneContainer.paneForUri(uri)
-
-  # Public: Get the active {Pane}'s active item.
+  # Essential: Get the active {Pane}'s active item.
   #
   # Returns an pane item {Object}.
   getActivePaneItem: ->
-    @paneContainer.getActivePane().getActiveItem()
+    @paneContainer.getActivePaneItem()
 
-  # Public: Save the active pane item.
+  # Essential: Get all text editors in the workspace.
+  #
+  # Returns an {Array} of {Editor}s.
+  getTextEditors: ->
+    @getPaneItems().filter (item) -> item instanceof Editor
+
+  # Essential: Get the active item if it is an {Editor}.
+  #
+  # Returns an {Editor} or `undefined` if the current active item is not an
+  # {Editor}.
+  getActiveTextEditor: ->
+    activeItem = @getActiveItem()
+    activeItem if activeItem instanceof Editor
+
+  # Deprecated:
+  getActiveEditor: ->
+    @activePane?.getActiveEditor()
+
+  # Extended: Save all pane items.
+  saveAll: ->
+    @paneContainer.saveAll()
+
+  # Save the active pane item.
   #
   # If the active pane item currently has a URI according to the item's
   # `.getUri` method, calls `.save` on the item. Otherwise
@@ -286,7 +376,7 @@ class Workspace extends Model
   saveActivePaneItem: ->
     @activePane?.saveActiveItem()
 
-  # Public: Prompt the user for a path and save the active pane item to it.
+  # Prompt the user for a path and save the active pane item to it.
   #
   # Opens a native dialog where the user selects a path on disk, then calls
   # `.saveAs` on the item with the selected path. This method does nothing if
@@ -294,34 +384,59 @@ class Workspace extends Model
   saveActivePaneItemAs: ->
     @activePane?.saveActiveItemAs()
 
-  # Public: Destroy (close) the active pane item.
+  # Destroy (close) the active pane item.
   #
   # Removes the active pane item and calls the `.destroy` method on it if one is
   # defined.
   destroyActivePaneItem: ->
     @activePane?.destroyActiveItem()
 
-  # Public: Destroy (close) the active pane.
+  ###
+  Section: Panes
+  ###
+
+  # Extended: Get all panes in the workspace.
+  #
+  # Returns an {Array} of {Pane}s.
+  getPanes: ->
+    @paneContainer.getPanes()
+
+  # Extended: Get the active {Pane}.
+  #
+  # Returns a {Pane}.
+  getActivePane: ->
+    @paneContainer.getActivePane()
+
+  # Extended: Make the next pane active.
+  activateNextPane: ->
+    @paneContainer.activateNextPane()
+
+  # Extended: Make the previous pane active.
+  activatePreviousPane: ->
+    @paneContainer.activatePreviousPane()
+
+  # Extended: Get the first pane {Pane} with an item for the given URI.
+  #
+  # * `uri` {String} uri
+  #
+  # Returns a {Pane} or `undefined` if no pane exists for the given URI.
+  paneForUri: (uri) ->
+    @paneContainer.paneForUri(uri)
+
+  # Destroy (close) the active pane.
   destroyActivePane: ->
     @activePane?.destroy()
 
-  # Public: Get the active item if it is an {Editor}.
-  #
-  # Returns an {Editor} or `undefined` if the current active item is not an
-  # {Editor}.
-  getActiveEditor: ->
-    @activePane?.getActiveEditor()
-
-  # Public: Increase the editor font size by 1px.
+  # Increase the editor font size by 1px.
   increaseFontSize: ->
     atom.config.set("editor.fontSize", atom.config.get("editor.fontSize") + 1)
 
-  # Public: Decrease the editor font size by 1px.
+  # Decrease the editor font size by 1px.
   decreaseFontSize: ->
     fontSize = atom.config.get("editor.fontSize")
     atom.config.set("editor.fontSize", fontSize - 1) if fontSize > 1
 
-  # Public: Restore to a default editor font size.
+  # Restore to a default editor font size.
   resetFontSize: ->
     atom.config.restoreDefault("editor.fontSize")