The users want to know it is actually doing something and not just stuck saving or whatever, lest they be tempted to do something because it has been broken. In particular TC takes some time to save files and sits there "doing nothing" which is annoying, at least to one tester who provided feedback. I have a progress bar that helps somewhat - if you can update a progress bar in the middle of a file save, that would be a viable alterative, I think. Some other operations take over a minute.
When it is "doing things" controls are greyed out (inactive) so they can't do anything. I've been told that if it looks like it is doing nothing for over three minutes, a tester will be greatly tempted to shut it down and start over because "it is obviously broken - if it is still working, make it look like it is doing something."
I have to address this in my response to review comments.