I've been a Gmail user since its invite-only inception. I would agree with you about the UI a year ago. But the new SMS-sized compose window and the UI changes that put all non-basic functionality 2 or 3 clicks away are really annoying.

I would leave Gmail due to the UI changes, although I must confess I hadn't at the moment because it's too much bother to tell people about a new address, set up redirection, find out how to save all the old messages and have them at hand, etc.