By now, many of you know that Portal 2 on PlayStation 3 will take advantage of Steam. The main selling point has been, so far, that buying the game for PS3 automatically gets you the PC and Mac versions at no extra cost to you. Pretty slick deal, but now we have more to go on.
Essentially, we're getting cross-platform everything -- matchmaking, friends, chat, and achievements. Plus, co-op and single-player saves alike will be sent to the cloud, meaning your progress is remembered on any PS3; unfortunately, you can't pick up the same save on PC/Mac.
Interestingly enough, the Steam overlay shows your PlayStation Network friends, in addition to your pals on Steam. Previously, Valve mentioned its hope that future titles will offer similar Steam compatibility. Make it so!