Well, I use Vista, and I've had no compatibilty problems. There's a perceived "incompatibleness" about vista that is simply not true. I've thrown everything at vista and it's run everything. Sure, they're be a handful of titles that will have a few problems (like 1%), but the so-called teething problems that people were expecting Vista to exhibit have been unfounded. It's been designed for backwards compatibility.
Vista is not simply XP with a few bolted addons. It's a complete refurb. New Network comunication stack, far far tighter security, in my experience far far more stable (Drivers have to be developed to comply with strict guidlines, especially Graphics, unlike the looser XP specs.) and will be the defacto OS in only a few months time. XP support will gradually deminish and all new software will be developed with vista in mind.
Why bother buying XP when you can get Vista for the same price. The difference below the hood (like the stuff you won't even notice) is worth the change over for security and stability sake. Even Basic Vista is better over XP. So what if it doesn't have Aero - duhhh, nor does XP!
Vista has been around for enough months now that most hardware and peripherals have Vista drivers. Just check that there all supported, and go the Vista route. No point going backwards, even if it's for the sake of 6 months, is it?