The transition to Linux has made the Steam games 16 % faster on Steam OS than under WIndows.
The transition from DirectX to OpenGL has given a surprisingly big advantage:
After this work, Left 4 Dead 2 is running at 315 FPS on Linux. That the Linux version runs faster than the Windows version (270.6) seems a little counter-intuitive, given the greater amount of time we have spent on the Windows version. However, it does speak to the underlying efficiency of the kernel and OpenGL. Interestingly, in the process of working with hardware vendors we also sped up the OpenGL implementation on Windows. Left 4 Dead 2 is now running at 303.4 FPS with that configuration.
This simply means that Linux and OpenGL is better than MS and DirectX for Gaming - who would have thought....
So if you want your Zombies to move faster; a Steam box makes sense. The hardware and software is optimized for the game there.
And the Steam box is a non spying open source box.
The Valve contributions to the drivers will be shared with the Linux community - so it will work fine as an install under (any) Linux too.
The developers are happy that developing is more efficient on Linux than on Windows