addresses suggestions from pull-request

atom/browser/api/lib/auto-updater.coffee

@@ -1,8 +1,9 @@
 switch process.platform
-  when 'darwin'
-    autoUpdater = process.atomBinding('auto_updater').autoUpdater
   when 'win32'
-    autoUpdater = require('./auto-updater-win')
+    autoUpdater = require('./auto-updater/auto-updater-win')
+  default
+    # take the default binding for the current platform
+    autoUpdater = process.atomBinding('auto_updater').autoUpdater
 
 EventEmitter = require('events').EventEmitter
 

atom/browser/api/lib/auto-updater/auto-updater-win.coffee

@@ -7,7 +7,10 @@ class AutoUpdater
   quitAndInstall: ->
     # TODO
 
-  setFeedUrl: (@updateUrl) ->
+  setFeedUrl: (updateUrl) ->
+    # set feed URL only when it hasn't been set before
+    unless @updateUrl
+      @updateUrl = updateUrl
 
   checkForUpdates: ->
     throw new Error('Update URL is not set') unless @updateUrl

atom/browser/api/lib/auto-updater/squirrel-update-win.coffee

@@ -2,8 +2,8 @@ ChildProcess = require 'child_process'
 fs           = require 'fs'
 path         = require 'path'
 
-appFolder             = path.resolve(process.execPath, '..') # i.e. my-app/app-0.1.13/
-rootApplicationFolder = path.resolve(appFolder, '..') # i.e. my-app/
+appFolder             = path.dirname(process.execPath) # i.e. my-app/app-0.1.13/
+rootApplicationFolder = path.resolve(appFolder, '..')  # i.e. my-app/
 updateDotExe          = path.join(rootApplicationFolder, 'Update.exe')
 exeName               = path.basename(process.execPath)