Steam for Linux is soon to be in external beta and doing very well thankyouverymuch. Gabe Newell had it designed as a nuclear bunker of sorts, for Valve to shelter in should the worst happen - i.e., should Windows 8 mark the first point in the deterioration of the PC as an open platform.
Happily though, it’s also looking really good. Left 4 Dead 2’s zombies actually run faster on Linux, and a glance at the data strings reveals that Valve are readying a Team Fortress 2 beta as its next release.
The strings picked up at CDR Parser reveal the insides of Steam’s Content Description Record on Linux, which features repeated reference to a Team Fortress 2 beta, as well as a link to this manual for the Engineer’s sentry.
Frankly, I’m not sure I can handle Team Fortress 2 any faster than it is on PC. In Left 4 Dead 2’s case, the cause was some "microsecond overheads per batch" in Direct3D that don't exist in OpenGL, so it’s not unfeasible that the same will apply here.
Are you one of the fortunate few in the Steam Linux beta? Let us know how you’ve been getting on.