I still wonder why OpenGL? Its so much more inmature than DirectX... The only reason i can find is that dx is exclusive to windows and maybe opengl is more flexible in suggestions and bug fixxes.
but really: why opengl???
OpenGL is not immature, the drivers are (of ATI and Intel). They are immature because majority of games use DirectX, but the situation is different for simulators, especially in military. As far as the API is concerned, in my opinion OpenGL works better, has less overhead and allows us to use the GPU in better ways.
However, the winds are changing also in gaming. Microsoft is trying hard to kill itself, ballmering down for a long time and becoming less and less competitive. New OS for tablets all use OpenGL (ES), it looks good for the future of OpenGL.
Why we decided to go for OpenGL back when it was not so clear ... because DirectX is Windows only (and we want portability), because M$ subjects it to their marketing strategy (see the decision not to enable newer versions of DirectX in previous OS versions). Because we want OT to survive the decline of the empire.
Besides, I believe that there would be problems even on DirectX (with the drivers). Majority of games use DirectX, but they also use just a small subset of new functionality of graphics units.
Still, the situation with AMD bothers me.