Apple is promoting OpenCL and GPGPU acceleration of programs which to my mind is a big plus for the forthcoming Snow Leopard but at the same time the graphics hardware that you can put into the Mac Pro is severely limited. Nvidia's Tesla C1060 won't work under OS-X (EFI issues I think) and the currently available graphics cards are limited to 512M (under OS-X). My interest is for scientific simulation software (eg electromagnetic simulation etc) but I realise that for the majority of Mac Pro users, the only question is whether or not Adobe makes use of it in CS5 (or whatever the next release is), but even here if Windows users get acceleration from graphics cards with 3 to 8 times the gpu RAM available and Windows adopts openCL at some point Apple will be left behind. I am still sitting on the fence wondering whether to jump into the exciting Apple/OS X camp or whether to stick with boring but relatively safe Windows/Linux. I know bootcamp gives you a choice but I get the impression that when it comes to things like installing a Tesla C1060 there are problems even under Windows/Linux because of EFI. (I may be wrong, this is just my impression from things like the Tesla forums on nvidia's site.) My worries are Apples resources for development are allocated in a priority that goes iphone/ipods etc > lap tops > iMacs > Mac Pros for Graphics Professionals > Mac Pros for nerdy scientists and nvidia etc aren't going to put their resources in if Apple isn't.