Comment 4 for bug 387934

So the use cases should be as follows

Window Opens:
   * File name field has focus

Single Click on a Folder:
   * Folder has focus

Double Click on Folder:
   * Navigate to folder
   * Return focus to file name

Over all 90% of the time the user will be changing folders to change its location then change its name.

Of course this is just my opinion but how I would expect it to work.