R600g driver is almost as fast as AMD Catalyst, even without the new back-end: http://www.phoronix.com/vr.php?view=19048
Nouveau for Nvidia at least for GTX300 and before, is also in a good state. Intel's to.
It will be good to have a D3D state tracker installation from PlayOnLinux, plus a patched Wine with other patches to (like awesomium).
I believe these things will be in fast development state inside 2013. Intel and Mesa people have decided for an OpenGL version release every 3 months instead of 6, and also to update Mesa version releases every 15 days.