I thought I'd give KDE a try after wanting something a bit prettier than LXDE, and Gnome 3 and Unity not being to my tastes.
I'm actually really surprised, I never thought I'd go back to KDE. I was an avid KDE 3.5 user, and I dropped KDE after KDE 4 was released - for obvious reasons.
But KDE 4.6.2 (the one I'm running) seems so much more polished than the original KDE 4. I'm really impressed with the desktop widgets, and generally how responsive it is - far, far more responsive than Unity or Gnome 3. Especially good considering I'm running on an old Dell D420 laptop.
Although, I can't stand the 'bouncing' icon whenever anything is launched. In my opinion it's incredibly tacky, and has no place on my desktop
Overall, though; I'm very impressed.