If graphics performance is even a concern, who cares its on a 22nm die and can be overclocked to hell and back.
I'd agree, but there are several problems:
1) Mac users are generally noobs without a clue on how to overclock, swap hard drives, flash roms, etc. Development for such fine-tuning computer savvy people would be limited on the mac side.
2) GPU Drivers for OS X? I've never seen a single overclocking utility for any graphics card on a mac.
3) Overclocking still works best in Windows.
4) Anyone actually buying a mac to play games or do 3D work in OS X is crazy. Windows runs OS X into the pavement in this area, especially in gaming.
5) Graphics cards have always sucked hard on every macintosh computer and any 3rd party upgrade for the Mac (in this case, the mac pro, because apple doesnt believe in choice for iMac users) has always been expensive and to make matters worse, the offerings have usually been obsolete last generation.
Thats not to say I wouldnt like to see better gpu support for macs. If I could play Half Life 2 ep. 2, portal or other games at 1920 x 1200, 4X FSAA and maximum settings getting a constant (and minimum) 60fps, I'd be real happy.
But the reality is this: gaming and graphics cards are a complete pathetic JOKE in OS X. And anyone who disagrees is in denial.