Vista is nothing to be worried about upgrading to - id say 98% of compatability issues have been solved (2% owed to creative, but thank god for daniel_k). People who moan and go on about how vista sucks and what not clearly either are going with the rest of the crowd or just havent used it. I went from XP M.Center to Vista home premium 32 bit and i cant imagine using XP again - Vista looks better, is more stable, as many have said boots and loads things faster, and overall is a better OS.
I downloaded the 64 bit version of Vista Ultimate to check compatability, and found that the only thing that did not work was my USB wireless device. I dont have another, so i reinstalled 32 bit home premium. That said, when i go intel for my Q6600, ill purchase the newer model of my USB stick and also get another 2GB of RAM, along with a legitimate version of either 64 bit home premium or ultimate. Basically as everything progresses, you cant stay true to an older thing for too long, because the benefits of the newer item just outweigh old familiar.
Basically, ignore all the XP diehards, go for the 64 bit vista and i promise you, you will not look back.