OS X is too closed of a platform to get anywhere for gaming. No one's gonna pay three times the cost of the hardware, and then deal with inferior performance as well. If Apple cared about gaming (or even trying to get marketshare above the single digits, really), they'd license it out like Microsoft does... but I'm sure they're happy duping the unwashed masses with their propaganda and making shittons of markup on their machines.
It's nice the Valve ported Steam and some of their games to Mac, but I don't think it'll serve as anything more than for the few gamers who own Macs to not have to boot up their Windows machines, or reboot into Windows, in order to play them. I just can't see anyone going out of their way to buy a Mac for gaming. =
And on an unrelated note, today, we're playing Steam!