This looks like good directions for dual-booting, with XP and Linux, then Vista with Linux installed first and Linux with Vista installed first.
I'm betting there is going to be a lot of dual-boot Vista setups, as those who have to support it put it on machines where it won't get in their way most of the time. I, personally, am not going to dual-boot again, ever, I hope. I'll dedicate a machine to Vista. I don't have too much problem with that. But not everyone feels the same way, so here is the information you need if you're so inclined.