Valve made a lot of noise at Sony’s E3 2010 press conference when studio founder Gabe Newell took the stage and announced that Portal 2 for PS3 would ship with Steam support, implying that users of the PS3 version would have access to the usual suite of Steamworks features, including the Steam Cloud, achievements, and various friends list functionalities. And, yeah, this is all true: in a press release floated by Valve this afternoon, the studio detailed all of the stuff you’ll be able to do in the PS3 version with a connected Steam account, specifically stating that users, via a version of the Steam UI overlay, will be able to access their Steam friends list, chat with other Steam users, accept and send game invites cross game, view Steam achievements, and send their save files to Steam's cloud for PS3-to-PS3 transfer.
The Steam integration sounds like a dream, but when you start to break it down, it might not be quite as useful as it initially sounds. For starters, the save games aren't compatible across platforms, so your cloud-based save for the PS3 version won't pipe into the PC/Mac release. Perhaps that was a bit much to expect in the first place. Of course, PlayStation Plus subscribers already have cloud-based save storage across all PlayStation 3 games. Also, since the PS3 version of the game will tie into your Steam account, you won't be able to use your free PC/Mac copy to play co-operative games with only one copy of the game.
The Steam integration sounds like a dream, but when you start to break it down, it might not be quite as useful as it initially sounds. For starters, the save games aren't compatible across platforms, so your cloud-based save for the PS3 version won't pipe into the PC/Mac release. Perhaps that was a bit much to expect in the first place. Of course, PlayStation Plus subscribers already have cloud-based save storage across all PlayStation 3 games. Also, since the PS3 version of the game will tie into your Steam account, you won't be able to use your free PC/Mac copy to play co-operative games with only one copy of the game.
Anyway, all of these Steam features will require a Steam account linked with a PSN account, so you’ll need both to take advantage of these networks to use the Steam overlay. It sounds like Valve is making account creation easy for you PS3 owners, too. You'll be able to get yourself a Steam account directly from Portal 2.