I wonder if Apple will address the issues this 3D pro has with the GPUs:
http://arstechnica.com/apple/2013/06/a-critical-look-at-the-new-mac-pro/
"Because it's so obviously a custom part that I doubt will be user-upgradable, this left a pit in my stomach after the WWDC Mac Pro talk. I work as an art director and a 3D artist, and this prospect of never being able to replace the video card freaks me out. I dont care about gaming on the Mac ProI have a PC and a PS3 for thatbut having the same GPU for four years (typically how long I keep a Mac Pro) is not appealing."
And:
"As for what to expect performance-wise, its hard to say since the last iteration of Radeon 7950 for Macs was a huge letdown for me. In my experience with apps like Maya and Cinema 4D, it came nowhere near the performance with pro apps that you see in Linux (fastest) or Windows (fast) with the same 7950. A dual 6GB GPU with OpenGL 4.1 support (coming in OS X 10.9) would do much to address my concerns about long-term shelf life for 3D on the new Mac Pro, but Apple and AMD need to address OS Xs driver performance shortcomings, because they are significant. Once the hard work of getting tessellation and other OpenGL 4.1 features is done, I really hope they start honing GL speeds in OS X because the last thing I want is a slow video card with lots of video RAM and a fancy namefor four years.
But many 3D users arent even going to get to the point of using the new Mac Pro. The fact that the GPU is not user-replaceable remains a huge issue for people like me, and this is going to do a lot to send potential Mac Pro 3D users to Windows PCs. If there are only good/better/best purchase options, with the GPU and the CPU speeds linked for build options on the Mac store, that would further limit our options. I really hope theres some freedom on the configuration end, since I usually buy a top-end GPU but the mid-speed Xeon."