I use:
- Dual 800 PIII running NT 4,
- PIII 650 Laptop running Win 2K
- P4 2.26 running Win 2K
- sometimes use a Celeron 600 laptop XP
- Celeron 667 running Linux
- Power Mac dual 867 with 10.2.4
Of the Microsoft OSs, I like Win 2K the best. XP, I like the feature on multiple users at the same time. You don't have to close all your windows and logout to login as another user. But XP is like too much sugar. The final reason for not using XP is the license agreement (EULA).
I wouldn't recommend using dual processors under Windows. My back up software (retrospect) was very good at locking up my dual processor NT machine.
I rate my Linux box and Power Mac as equivalent for stability. But OS X is much more usable. If I bring up a "pdf" file on my OS X and Linux box, it VERY clear to see the difference. If someone wants to run a *nix OS for a desktop machine, I recommend get OS X.
OS X vs Windows vs Linux.
I think Apple has taken a balanced approach to the OS. I think they have made the kernel more responsive. More like a Real Time Operating System (RTOS). I think Windows tendancy is to give a program (task) more priority.
The reason I think this is that is that if you run a Quicktime movie or Realplayer (or the like) (even winamp and music only).
On the Mac (or any Mac I have used), the movie plays without a stutter, even if you run something intensive in the background.
On my 2.26G P4 with Win 2K, a movie will stutter (pause for a brief but preceptable time). This I find unacceptable.
Sorry for making this so long.

(yawn)