The 2006 Mac Pro with the dual 2.66 Xeon CPU's was the best computer I had ever owned. Reliable, upgradable, and a fantastic performer. I had an ATI 5770, 12 gigs of ram, and an OCZ Vertex 2 SSD drive. The machine handled pretty much what I threw at it, with no slow down or issues. Games like starcraft 2 and Diablo 3 played with pretty much the highest settings. I did not a few issues with the WiFi and bluetooth connections at first - but after a while of tinkering and switching wires around, I was able to get it to work well. Now, enter the 2009 Mac Pro. Given that the 2006 Mac Pro will likely not support Mountain Lion, I decided to upgrade to a new Mac Pro. Newer 2.66 CPU's, quad core version. 16 gigs of ram - much cheaper to buy ram. 16 Gigs from OWC cost me $150, while for the 2006 Mac Pro 12 gigs was hundreds more. I popped in my SSD drive, and ordered up an ATI 6870 card running an Apple 24 inch LED display. This computer is super fast - even more so than the 2006 Mac Pro I loved. It did not come with WiFi, so I bought the card and installed it myself. In the beginning, I had issues with bluetooth again, but they were resolved by moving my Magic Mouse closer to the Mac Pro case. The internet speeds are much faster too. I have an "N" router, and my 2006 Mac Pro's internal Airport card always seemed to have less range and be a bit slower since the router is in another room. The 2009 Mac Pro's card, which I believe is "N" now as well - has much better range and is much faster. Feels like it's connected with Ethernet. Overall, a definite great upgrade - I think this machine will last me a few years since Apple is unlikely to make it obsolete anytime soon since it shares so much with the 5.1 Mac Pros. I thought about getting the new iMac - but hey, I just love the Mac Pro and it feels so much more robust, plus it's so upgradable. The iMac is difficult to really upgrade unless you start to go crazy with it.