When my XP box died and I couldn't get office etc. to install due to licensing issues, I moved to Ubuntu 5.1. It worked and the kids liked it but something went wrong (bad hard drive I think). Anywho, the box sat for a while and I just got around to downloading Ubuntu 6.1. WOW! Ubuntu has gotten even better.
It's still linux so getting the latest NVIDIA installed and working is not push button easy. But I can't wait to try XGL/Compiz. Unfortunately, my daughter was very excited about Ubuntu being back. So she's in the interweb playing some flash games.