I had a RAID0 array on my current build when I was using Vista. It was extremely easy to set up, all I had to do was go into the RAID utility, tell it what type of array I wanted, and change a few settings, and then I was ready to go. Vista installed without a hitch, and I noticed a decent improvement when loading games and transferring my large videos and photos.
Although I was messing around in Linux and I messed up the drive while trying to create a partition, so everything was lost (luckily I make backups on DVD's though). I would have run a RAID0 array again with XP, but I dont have any drivers for it so XP doesnt recognize the array. So now I have one drive setup for my data, and the other for the OS.