So I downloaded Steam for Mac a couple days ago, along with Portal. I had played a demo version a while back via Boot Camp and I was quite excited about being able to pick it up for free on the Mac now. (I would have bought it before if it wasn't PC-only.) Needless to say, I was quite shocked to find out that my iMac (24" iMac, 2.16ghz C2D, Nvidia 7600GT) didn't meet the minimum system requirements. After all, I had indeed played it before on the same machine, via Windows XP.
A quick trip to the Steam Forums gave me an explanation. The drivers Apple supplies for Nvidia 7 series GPUs are out of date and don't support a function that Valve's Source Engine relies upon. To any Windows user this simply means "Download the latest drivers." Unfortunately, for Mac users it means "Pray that Apple hasn't deemed your hardware obsolete yet and hope they update the drivers in the next OS revision." Needless to say, I have a bad feeling that my three-and-a-half year old iMac has past the point of irrelevance in Apple's eye.
While I understand (and often appreciate) that Apple doesn't tie itself down with legacy support, it would still suck to be the other side of this particular chopping block. The fact that I can reboot into Windows and run these games just fine (or even run the Windows versions on the Mac side via Crossover) reflects poorly on Apple and OS X. Heck, on the PC side you can play these games on Nvidia 6 series cards!
Steam coming to the Mac is a huge deal …it would truly be sad if Apple turns their back on this issue simply because the hardware is a few years old.
PS: Starcraft II looks to be another casualty on my iMac (along with every other Valve/Source game) if Apple doesn't update the drivers.