I'm primarily a PC guy, but I've used Macs over the years.  My latest addition is an iMac with a 20 inch monitor and built in hardware.  It's a piece of art as much as hardware.  I miss the 747-like CPU fan on my PC like a rash.  Here's a quick summary after two weeks of how things stack up, on one view:

To the Mac:

1) Style - it's not just a meritocracy - remember Jaguar?

2) Hardware integration - nothing to think about - nothing.

3) Music and video editing - brillant built in applications and hardware integration

4) Shell access - it's Linux

5) User interface - a slight edge here

6) Performance - partly to do with less software availability, but generally true 

7) Form factor - I now live with less noise, wires, plugs, etc.

To the Vista PC:

1) Software - there's lots more of it

2) Programming - you're boxed in to web apps, Objective C, or sometimes updated Java on the Mac

3) Office - it doesn't compare on the Mac

4) Reliability

 I don't think there's anything remarkable here, expect #4, and I'd say that's the the primary reason I won't start buying iMacs for the office.  I've "Forced Quit" too many times over the past few weeks for my liking.  I think there is a misperception that apps written for OS X are more stable, but I'd say, anecdotally, that this is not true.  Among the crashers: mail, XCode, and Firefox.  I believe I managed to crash the OS as well.  (Grey screen, giant apple, hardware unresponsive)