I have been a mac user for 10 years (and an Apple II user prior to that).
I still never moved over (in my head) to the drastic changes in OS X. It's evidently *exceptionally* customizable, with the prerequisite knowledge of unix (or linux, I dunno...shows you what I know).
OS X is incredibly stable, big deal. If you know what you are doing, WinXP is stable too.
Macs, as someone mentioned, integrate very well. The iLife suite allows you to rip mp3's, put them on your iPod or burn them to a CD, or you can open up iPhoto, and create a photo cd using your images and songs from iTunes. Same goes for iMovie, which I find to be an amazing program. I used to encode old VHS tapes from my VCR on my mac, which was too easy. Editing, cleaning, adding audio, adding titles/washes, iMovie is an awesome program.
The big hangups about Macs are twofold (but there is an upside). First is that Microsoft Office has not ported Access (part of the Office suite) to Mac. Ever. I use a Dell laptop for a reason, and Access is one (SPSS and SAS are the others, though SPSS is available for Mac). I really like Access, and, although there is a database prog for OS X (FileMaker Pro?), it just isn't Access.
The other downside, of course, as many have mentioned, is the lack of games. You can see the desolate state of Mac gaming at
http://www.insidemacgames.com
The upside to the poor state of mac gaming? Longer shelf life! I bought my PowerMac G4 (for sale on eBay now, though 'taint cheap) in April of 2001, so it's almost 3 years old, and I've had no problems running any programs on it (except the pisspoor programming at SPSS makes its mac version neigh unusable). I can't speak for PC users, but I know I would have a tough time running HL2 or Doom 3 on my current Dell laptop (EDIT to point out that said Dell laptop is 13 months old). One's PC may last for 3 years, but not without substantial upgrades to be able to run certain games; a good mac will last you, upgrade free ('cept for storage space, of course) for much longer, in my view.
myke.
...let the refutations begin.