Engadget has posted a quick preview piece of Steam for Mac, which comes out in two days!
"It's practically the exact same as the Windows version, except there's almost nothing to buy. Save for the Growl-like notifications at the top of the screen, the UI is all but indistinguishable, and as promised,data and purchases (if playable) automatically carry over in their entirety from your Windows Steam account."
This is encouraging news to be sure, although framerates aren't 100% there, they are close and those with slightly older laptops might run into some problems. Full details can be found on the source link!