I dunno, 2000 server with the service packs... very stable.  2003 server so far has been solid in my experience.  We are running about 20-30 of them in the company I work for, so far its just been the third-party craplications that have done anything bad to em.  My guess would be hardware failure or an error in setting up the software, or third-party software if there is any difference in stability.  I mean, granted if you run any box running no GUI on top there is gonna be less mem util.  Whatever.  Use Linux if it makes ya horny.  More power to ya.

I wish I could speak from experience with the new Macs, but I'm honestly impressed with what I've read on the new G5s and on OSX in general.  Can't say I've ever used one though.  Heck, I don't even know anyone that actually OWNS one.  I would venture to guess they are still very sold video editing machines, and generally user-friendly computers (for casual end users who dont want to ever change any settings at all).  And they look so purrrrrdy!!!! =P  I think Lian Li should make one that looks a little more like it.  This one just doesn't cut it...