DX9 support is still experimental and requires an unstable Wine fork to make it run.
I have to say I managed to have it working and I got a 50% increase in FPS in Steam/Source games running under Wine.
There's the "old" DirectX -> OpenGL translation layer in Wine but it is not really efficient or performant, although it may be enough for GUI applications.
>> There is DX9 support on Linux and IIRC a partial DX10/11 implementation bit-rotting somewhere.
Sadly Gallium3D isn't "Linux" yet. It's only really usable on AMD open source drivers that is very small portion of market and I would say it's 15% at best, but in reality likely 5-10%.
What version? There is DX9 support on Linux and IIRC a partial DX10/11 implementation bit-rotting somewhere.