This is a big turnaround for me however because it is not that long ago that I would have sworn never to use KDE. I last tried it over 10 years ago and thought it had a lot of very rough edges, plus felt and looked "cheap". Alongside too many half-baked "K" applications and a ridiculous number of configuration parameters and settings, a significant part of it didn't work very well.
It's completely different now and the Debian Wheezy version I'm using (KDE 4.8.4, a few versions out of date now) not only looks fantastic but almost all of it works as expected.
I've had it crash once whilst messing with a particular desktop setting, but it restarted itself automatically and carried on from where it left off. In comparison, I booted Gnome 3 a few weeks ago, just to have another look, played with the ALT+TAB/ALT+` switching for a few seconds and it crashed the desktop. Unlike KDE, it didn't recover but logged you out, losing everything.
The desktop still has a lot of settings to browse but the control panel makes sense and it all seems properly integrated. There are still a few areas I don't properly understand, KDE activities being the main one, but you can ignore them until you feel like having a better look. Virtual desktops work as usual.
All in all, I'm really liking KDE. The developers are doing a wonderful job and the QT toolkit gets better and better. Definitely worth a look.
For people that want to have a play themselves, you can download a KDE live DVD (e.g. Suse do KDE well), boot from it and play without affecting or changing anything on your PC.