Valve has announced that there will be a private beta for Steam on Linux this october. 1,000 external users will take part. The beta test will be hold sometime in october. The beta will include the Steam platform and one Valve game (L4D2 or Portal). Steam's 'Big Picture mode' will not yet be supported, nor any other games.
The internal beta will start next week.
Update: There is some speculation going around about which game the beta will include. It will probably be Left 4 Dead 2 - not Portal, because the Valve Linux team answered one of the comments with: Owning a copy of L4D2 will not affect your eligibility for the external beta.
Good thing that I am also running Ubtuntu Linux. I am looking forward to this especially because of the fact that games tend to run faster on Linux than on Windows. It depends on the ports though, I guess. I mean, GTA 4 was a poor PC port anyways ... . I´ve heard that a "new" patched improves performance but I haven´t tried it out yet.
It's been a long time coming but I'll not complain. Still not sure if I can live with out ArmA and Dayz... Win7 may have the hang arround for a little while longer...
I'm not convinced it will be L4D2, I do know they already have L4D2 dedicated server for linux. But that was the first comment.. so he either has inside information, or he's just making a broad assumption.
Also, on previous posts they talk about L4D2 being developed for Linux, but they make the statement, "one valve game." which is either Misdirection, and it will be L4D2, or they are quite serious, and it could very well be CounterStrike. (or half life 3 LOL)