Someone mentioned it earlier...
Have you ever tried to sell a used Windows machine? You can't give them away after a year

I was a Windows user for 20 years. Switched two years ago and I can't imagine EVER owning another PC again. My '08 Mac Pro is the fastest, most stable and efficient system I have ever used. My computers are a direct reflection on my bank account and the money I can make. It pains me to know I waited as long as I did to make the switch. Creative should ONLY be done on the Mac (OSX) platform, if for nothing but peace of mind and Speed! The Holy Grail. I have never lost a project, gotten a virus, experienced the inevitable Windows "Slow down" due to time, etc. Couldn't be happier and I am glad to pay the price.
I think we'll see alot of the benefits from the Nahelm '09 crop of MacPros when SL releases in September. Both the 08 and 09 pros should fair well with an updated OS. Also, other software companies following suit to take advantage of the multiple cores as we see from both sides....the Multi physical and virtual core rigs. Compared to my G4 or my older Windows Quad cores....I am able to run FCP with Color, Motion, PS, and DVD Studio Pro while simultaneously surfing the web, checking emails, printing a 13x19 print and syncing my iPhone

No hiccups. What a machine to upgrade too

Pop the hard drive sled and mount a new one, slide it back in and power it on. New RAM, just as easy. Easy to clean out the dust with the cable management. Aesthetically pleasing....and third party vendors are ready to take care of your "Upgrades" for a reasonable price. All of my RAM and HDD shopping was done at OWC
Mac Pros are only over priced if you're buying it for the wrong reasons. It is a bit over kill as a home computer for surfing, email, even basic video and photography editing. BUT, if you are able to use to computer for a living and this will better your workflow, it is NOT over priced. (I am talking about the dual quads and the singles. Not every one needs all that horsepower). Peace of mind is invaluable in my world. I get that with Apple. And the Mac Pro is my most used tool in my inventory.
J