I switched from GNOME to KDE around the time 6.0 shipped, and I've been very happy with it. GNOME aims to be Mac-like but in my experience makes a lot of weird decisions. I've been on GNOME since 1.4 (2001?)
I had such a great time with KDE, and decided to promote it from just being on my "Linux PC" to all computers I own. I don't run Windows anymore, which is a nice feeling!