After having "upgraded" to Ubuntu Natty, the new interfaces were driving me crazy. Unity, in my opinion, is horrible. I couldn't configure it the way I wanted to, and I couldn't hide the top bar. I then switched to Gnome 3. Same complaint there. It would also change the background to a plain white background.
After a week of agony, I switched back to Gnome 2. I'm happy once more. You try to live in the future, you pay the price.