Just a refactored controller that uses a custom responder instead of those nasty respond_to blocks.

controller_made_by_unicorns.rb

class NotesController < ApplicationController
  self.responder = NotesResponder
  
  def create
    @page = Page.find(params[:page_id])
    @note = page.notes.create(params[:note])
    
    respond_with(@note, :location => page_path(@page))
  end
end

note_responder.rb

class NotesResponder < ActionController::Responder
  delegate :t, :flash, :to => :controller
  
  def to_html
    if resource.new_record?
      flash[:notice] = t("fuck_yeah")
    else
      flash[:alert] = resource.errors.full_messages.to_sentence
    end

    redirect_to navigation_location
  end
end

ugly_controller.rb

class NotesController < ApplicationController
  def create
    @page = Page.find(params[:page_id])
    @note = page.notes.create(params[:note])
    
    respond_to do |format|
      format.html do
        if @note.new_record?
          flash[:notice] = t("fuck_yeah")
        else
          flash[:alert] = @note.errors.full_messages.to_sentence
        end

        redirect_to page_path(@page)
      end
      
      format.json
    end
  end
end

# Tenho simplificado o controller mais ainda, fazendo o uso do padrão Command;

class NotesController < ApplicationController
  self.responder = NotesResponder

  def create
    @notes, @page = CreateNoteForPage.process!(params)

    respond_with(@note, :location => page_path(@page))
  end
end

class CreateNoteForPage
  def initialize(page_id, note_attributes)
    @page = Page.find(page_id)
    @note = @page.notes.create(note_attributes)
  end

  def process!
    {
      :page => @page,
      :note => @note
    }
  end

  def self.process!!(params)
    new(params[:page_id], params[:note]).process!
  end
end