Depends on OS developments. My 2006 Mac Pro is not supported under Mountain Lion, but it's still an excellent machine; 4 cores @ 2.66Ghz, 32GB of memory, and 6TB of disk. GigE, FireWire, USB, DVD/CDRom. I see no reason other than PC envy to upgrade to a different system. Eventually Apple will stop releasing security updates for Lion, and then I'll have to consider moving to a Linux distro. Short of a hardware failure I figure I'll get another 4-6 years out of it. Replacement parts for Mac Pros suck in price, but I bet I can find what I need on eBay. Heck, my system appears to be worth less than $500 according to my last search.