I have both. In fact, I have multiple copies of both. I took the Vista-plunge for professional reasons; I needed to learn how to use it. I hate to quote myself, but, to save myself a few keystrokes, here's a synopsis of my experience with the OS from several months back:
I purchased a copy of Vista Home Premium (OEM), so that I could learn how to use it. It's installed on a spare, 90GB partition of the system that I'm writing this post on. While it installed easily enough, I've found it to have all sorts of issues with peripherals and applications, everything from a year-old mopier to Adobe Reader. Honestly, it seems that EVERYTHING that I try do with Vista requires me to go online and research some sort of "workaround." This not an attractive quality in a world where folks with cash to spend can buy a Mac.
Technically, I hate it. In an environment where energy costs are soaring, M$ thrusts this resource hog on us, one that DEMANDS more wattage than it's predecessor, what with it's requirements for more RAM and VGA memory. Throw in a dual-core processor, and you're power bill is going up, trust me. With everything turned off, except Vista of course, my system's memory use idles at 508mb! I'm sorry, but there's simply no fit rationale for ANY OS to squander that level of resource, ON ITSELF. But don't worry, if you want to run Photo Shop, just throw in a couple of more GB RAM, and you're off.
Finally, there's sound, something which certainly impacts gamers. I'm not gonna give a detailed technical explanation of what Gates and company have done too it, but it's likely never gonna be as good as it was with WinXP. You can spend all the money that you like on a card, but Vista's software layer is so thick as to render the hardware acceleration that we're so fond of sort of mute. Microsoft claims that it was done to improve system stability by moving more of the sound API away from the kernal. I say, BS. It was done to improve DRM, at the expense of folks who paid for higher-end sound via parts like the Creative Labs X-Fi.
In closing, I've had Vista as an option on my system for about three months. About once a week, I login, look around and shrug my shoulders. It's certainly cute enough. I used to play one of the new games, (3D) Mahjong Titans, but stopped because it has a bug in it.
Since posting the thoughts above, I've actually played game demos on Vista,
Crysis,
Bioshock and
World in Conflict. While they run well enough, they run better in WinXP, with higher fps and much better sound. It's also worth noting that my gaming system is what could fairly be described as "muscular," having been built from about $1,800 worth of parts from Newegg computer. However, I still don't feel as though there's anything particularly revolutionary about Vista, excepting perhaps it's memory demands.
I still can't get over the fact that it takes 500+ megabytes of memory to boot into Vista. For that matter, the experience is a whole lot more like going from DOS to Win95 than going from '98 to XP. In both cases the interface was glitzier, but for a fair length of time, I couldn't do a hell of a lot with Win95, whereas XP allowed me to cache gobs of system memory, right off the bat. I didn't have a lot of problems with it as I'd already abandoned most of my old games that were written in 16-bit code.
I'm not sure where all this is headed, btw. I can say with considerable confidence that IT managers have NO interest in Vista. It uses too much electricity relative to the amount of work it does. YES, boys and girls, there's a price-tag for all that extra silicon and it's measured in kilowatts (which has a commensurate value in dollars). NOPE, they're gonna ring the last ounce of life out of 2000 and XP, and then look for something else, methinks, likely a Linux distribution. Time will tell.
PoE (aka ivanmoe)
Government is the opiate of the masses.
I believe in upgrading when one "has to" instead of when one is lead to by the nose. 
