Valve have released the details just ahead of Portal 2's official launch on the game's PlayStation 3 integration with Steam. PS3 owners will be getting a full Steam overlay, accessible by the select button, with integration of their Steam friend's lists, chat options, and more. In addition to these features, Valve reconfirmed that PS3 owners can play with Mac and PC owners of the same game in two player co-op - even better - if you earn any Trophies on your PlayStation 3 the corresponding achievement automatically unlocks on Steam. Sadly, earning achievements on Steam won't unlock the trophies on your PS3.
So what about the promised "free" copy of Portal 2 on Steam for PlayStation 3 owners? Basically you're given a one time use code that can be redeemed on the account you linked from your PlayStation 3 - it seems as though you won't be able to give that code to someone else as they'll have to have a PS3 copy of the game and a linked Steam account. Of course - there's no word on how this would work with a rental copy - details on that have not been explained on the official page.
Finally some details of Portal 2's co-op mode's story have been revealed. The story of two robots ties into the main story of the game and it takes place after the single player story. Thankfully, you don't HAVE to finish the single player to play co-op, its available from the start.
And now for the spoiler part of our show - we've got 7 minutes of Portal 2 footage that showcases the beginning of co-op.
If you still haven't pre-ordered the game, Amazon has it on sale for $54.99 with $20 of credit towards your next purchase. Portal 2 is out on Xbox 360, PlayStation 3 and PC on April 19th.