I know folks whose Macs haven’t died in over a year; having a proven BSD UNIX base in the OS definitely helps. 
My own uptime is a bit shorter, but only because my toddler decided the other day to turn off the Christmas lights by killing the entire power strip. :smack:
As for what Longhorn will be in 2006, just look at what MacOS X has now. 
Scalable graphics? Cross-application services? XML integration? We got all that two years ago…