The main goal of the AJAX mode is to reduce page reloads number for editing. However, current implementation has two events that needs page reloads: adding and editing resource/activity. This is very cumbersome when trying to create or update a large real course with 10-30 resources/activities.
The solution is to open create/edit page in new window and update the course via AJAX after adding or editing activity/resource.
I create improvement request MDL-13785 for this issue. Everyone who see this useful is welcome to vote for it (so it can get some attention from developers) and comment on it.