After using GNOME for two years, I decided to emerge KDE on my system this weekend. The reason being is I have been looking through the KDE source code for various projects here and there and I have been very impressed by the thought that went into designing such a large system. Everything is so well integrated and "just works" the way that it should. 3.2 is also hella fast.
There are some little inconsistancies in KDE, like some of the settings tools marked "Configuration" and some marked "Properties". The dialogs also have way too many options IMHO and when I open most apps it is a bit overwhelming to have so many options in the default dialog. I also miss the Ximian icons, and the beautiful Industrial theme.
KDE is excellent, though, and I plan on sticking to it. After two days I can honestly say that my productivity has gone up by using it.
Also, the documentation is excellent. The GNOME documentation leaves a whole lot to be desired and much of it is out of date.