Earlier today, Valve announced that its Steam publishing platform will support the Mac this Spring and I'm crazy-excited. With this, a large number of games based on the Source Engine will also be available on the Mac. (Yay, Portal!) I'm no news guys, but both Joystiq and Kotaku have a lot of great info.
The news comes less than a month after they started beta testing Steam's new UI, which is still rough around the edges, but now uses Webkit instead of Internet Explorer. (Yay, death-to-IE!)
What's that? You're a "Mac guy" and don't play games so why should you care? Firstly, hating fun isn't as cool as you hipsters think it is. Secondly, your favored platform just had the single largest digital distribution system for games fall into its lap. With Steam and Valve supporting the Mac, more games are most certain to follow, which is going to bring more users.
Steve Jobs has been full of empty promises about making Mac a gaming platform for over a decade and Valve just made that a real possibility. I couldn't guess at what kind of market share increase this could trigger, but I'm willing to bet it'll have a very measurable impact if enough game developers jump in the bandwagon.