TUAW posted a news story that OS X has gained 8% of the market share of the Steam platform

Valve has released the first Steam Hardware Survey since their Steam platform released for the Mac, and OS X has gained 8% of the market share already in its various iterations. Most of the Mac users are running 10.6.3, not surprising, given that those most likely to have the latest operating system are probably also the most likely to know that a Steam client is out and ready for them to download. Of course, the Mac faction still pales in comparison to the amount of Windows gamers on the network, but for a client that came out on the 12th day of the month for the survey data, 8% ain't bad at all.

  OS X grabs 8% share on Steam