There are so many crashes (return back to Windows without messages or warnings) that a backup before any manipulation (merge, flatten, the last one I was just scrubbing a clip with an audio file attached!) is always necessary.

So a quick save, I mean without the 3 secondes needed to create a thumbnail, accessible via a shortcut would be usefull. And as the undo option is also the cause of some crashes why not a revert option also.