Deprecated "best fit" detection is to difficult. Just provide a switch to toggle the new behavor on.

# new_rails_defaults.rb
  ActionController::Routing.generate_best_match = false

actionpack/lib/action_controller/routing.rb

@@ -271,6 +271,9 @@ module ActionController
 
     ALLOWED_REQUIREMENTS_FOR_OPTIMISATION = [:controller, :action].to_set
 
+    mattr_accessor :generate_best_match
+    self.generate_best_match = true
+
     # The root paths which may contain controller files
     mattr_accessor :controller_paths
     self.controller_paths = []

actionpack/lib/action_controller/routing/route_set.rb

@@ -406,24 +406,11 @@ module ActionController
 
           # don't use the recalled keys when determining which routes to check
           future_routes, deprecated_routes = routes_by_controller[controller][action][options.reject {|k,v| !v}.keys.sort_by { |x| x.object_id }]
-          no_worries = future_routes == deprecated_routes
+          routes = Routing.generate_best_match ? deprecated_routes : future_routes
 
-          deprecated_routes.each_with_index do |route, index|
+          routes.each_with_index do |route, index|
             results = route.__send__(method, options, merged, expire_on)
             if results && (!results.is_a?(Array) || results.first)
-
-              # Compare results with Rails 3.0 behavior
-              unless no_worries
-                future_routes.each_with_index do |route2, index2|
-                  new_results = route2.__send__(method, options, merged, expire_on)
-                  if new_results && (!new_results.is_a?(Array) || new_results.first) && index2 < future_routes.index(route)
-                    ActiveSupport::Deprecation.warn "The URL you generated will use the first matching route in routes.rb rather than the \"best\" match. " +
-                      "In Rails 3.0 #{new_results} will be generated instead of #{results}"
-                    break
-                  end
-                end
-              end
-
               return results
             end
           end

actionpack/test/controller/routing_test.rb

@@ -2191,10 +2191,8 @@ class RouteSetTest < ActiveSupport::TestCase
       map.connect "/ws/people", :controller => "people", :action => "index", :ws => true
     end
 
-    assert_deprecated {
-      url = set.generate(:controller => "people", :action => "index", :ws => true)
-      assert_equal "/ws/people", url
-    }
+    url = set.generate(:controller => "people", :action => "index", :ws => true)
+    assert_equal "/ws/people", url
   end
 
   def test_generate_changes_controller_module

railties/configs/initializers/new_rails_defaults.rb

@@ -11,6 +11,8 @@ if defined?(ActiveRecord)
   ActiveRecord::Base.store_full_sti_class = true
 end
 
+ActionController::Routing.generate_best_match = false
+
 # Use ISO 8601 format for JSON serialized times and dates.
 ActiveSupport.use_standard_json_time_format = true