To me, it seems that Valve probably sees this as a great opportunity to try to steal some of the PS3s userbase for their PC/Mac steam platform. Anyone who has played an fps with a mouse/keyboard combo knows how superior it is to console controllers, and once all the regular ps3 gamers start getting thrashed by PC gamers on the cross-platform multiplayer they'll know it too.

Now that they can switch to the PC, install steam, and improve their own game without having to buy another copy, valve has given them a serious incentive to give steam a chance.

The only problem is that, based on what I've seen so far, the portal 2 multiplayer doesn't seem that competitive or that dependent on twitchy control responses. If Valve were to do this with the next Call of Duty (a difficult deal to negotiate to say the least) or perhaps a Counterstrike sequel, they'd probably get a lot more switchers.