One of the main problems why the 'clean design' has not actually benefitted users is because of gmails feature creep. Where once I could just write and recieve mail, now, by default, I have 'stars', 'circles', 'importance markers', '+ share', 'notifications', 'gadgets'... etc. all confusing my view of my mail. Most users don't want any of these things, and they certainly don't want to have to spend mental energy realising they dont want them, then hunting around in settings menus to see if you can actually turn them off...

There are some good design additions in the revised gmail too, but IMHO the above is really what makes gmail feel much more cluttered and cumbersome than it was before....