I actually like Xubuntu best by a small margin over regular Ubuntu. At first I liked KDE due to its similarity to Windows' interface, but the more I use GNOME or xfce the more I like them. And every distribution I've tried KDE 4+ in I've had stability problems with (this could just be my hardware configuration, though - Vista gave me problems not everyone else had, too). Supposedly Xubuntu is for low-resources systems, but it sure seems adequate to me even though I've got far more resources than it requires.
Of the distros I've tried (mostly in virtual boxes), the *buntu's have definitely been the easiest to set up and get working perfectly, with Mandriva very close behind. Installing programs on many varieties of Linux is actually easier than on Windows thanks to package managers. And I have to admit that Ubuntu's graphics effects were impressive even inside a virtual box - Microsoft's PR people behind the "Wow" campaign for Vista clearly hadn't used Compiz Fusion enough.
Right now my primary Linux is split between Ubuntu and Xubuntu 9.04, which I really like now, and Mandriva 2008.1 with KDE 3.5, which I used earlier. I run them inside of VM's, though, so I always have quick access to Windows. Probably decreases the Linux experience a bit, but it's still decently good. OTOH, I was ready to switch to and very nearly did switch to Ubuntu back when I had Vista before I got XP. As I said, Vista didn't get along with my computer very well. Wish it had, as it would have saved me a lot of trouble, but at least I've had a working setup with XP for more than a year now.
Xfce is significantly less resource-hungry than KDE or Gnome. It's a great choice if KDE or Gnome have trouble with older hardware. If you want a real minimal desktop, but still with quite a bit of "WOW" factor, check out the FluxBox window manager. (I assume it's available in the *buntu repos.)

Personally, I like the KDE desktop. Lots of "WOW", easily configurable, etc. I currently run KDE 3.5.10 on my PCLinuxOS system. I have been playing with KDE 4.2 on my Kubuntu test system, though, and I think with the latest release (4.2.4) it is just about there. The desktop is better than the KDE3 one, and the associated KDE apps are almost up to where they should be.
Strider, have you had any luck with Civilization III on Linux with Wine by chance? I installed it and the editor works, but the game doesn't start at all - I'm guessing it's a CD protection problem.
An unfortunate fact of life: to play Civ on Linux under wine, you almost have to have a

pirated copy
