After reading this board over the last months, I actually was thinking of getting a pc desktop besides my powerbook. I slowly truly believed that windows isn't as bad as I remebered. That was until I used a pc over the last 2 weeks at work (I'm a freelance graphic designer and work 15-20 hours a week doing photoshop and illustrator stuff at a local company). I normally bring my powerbook with me, but a co-worker was on holiday and I was sitting at his desk. Remember this is a company pc which is looked after by an admin.
Ok, first, this thing is slow, very slow, it's a 3 ghz pentium 4 with 1 gig of ram running xp, and as far as I know shouldn't be any slower than my 1,67 ghz G4. But it is almost impossible to run illustrator and photoshop at the same time, I have to quit outlook and adobe reader before I even try it. On my pb I can run the complete creative suite + safari, ical, mail, itunes at the same time without any speed decrease.
Second, once you are used to expose & spotlight, file management without them is a pain. The search function in xp is painfully slow, at least on this machine.
Third, xp (and the screenshots I've seen of vista) look like it was designed by a colorblind designer. Blue - green - yellow, it could as well be a fisher price toy and it is really distracting when you are correcting colors in photoshop. Yes, I have switched to the "classic" look, at least this comes in neutral grey, but operating an os that looks like it's still 1995 is no fun either.
Fourth, apart from the color issue mentioned above, in photoshop, where every pixel of screen size is important, why must I have a top AND a bottom menu bar? The top bar in Os X that turns into the photoshop menu bar is a much more elegant and space saving solution.
Fifth, why can't I see how much hard drive space there is left on a volume when I have a window of it opened? This is some pretty basic information... why do I have to click something to get it? This seems so simple to do, is this something only I haven't figured out?
Please note that this is just my personal experience, as a long time mac user who has used windows for 2 weeks. I don't mean to start the same old discussion over and over again, I just wanted to share my story with the op, so that he or she knows what maybe is waiting out there in windows land.
Of course it's your decision, and whatever you pick I hope you'll be happy with it.
Personally, after this experience, I'll never think of getting a windows computer ever again, or at least until the next version after vista comes out in 5 years.^^