This story has been picked up and kicked around a lot lately, but I just had to post because of this part of the article:
In addition, the article revealed that Windows users who already have a Steam account will be able to re-download games using their existing keys on the Mac. If true, that means PC users could easily migrate to the Mac and play their favorite Valve games — including Half-Life 2, Team Fortress 2 and Left 4 Dead 2 — without having to buy them again for a new platform.
OMG, How cool is that?! Have a read of the rest of the article here: Apple Insider
MacRumors.com has just got confirmation on Steam release for April! See the story here: MacRumors.com