In the wake of the Vista and OpenGL issue I have been looking at C# the past month. Until recently, I had been doing development in Java because of it's multiplatform and has strong OpenGL support via JOGL. Using windowed OpenGL in Vista will incur a performance penalty since it is having to pass calls through to Direct3D. If developers need OpenGL 1.2+ they will have to drop out of WinFX and back to the older desktop. For full screen games this may not be an issue but for windowed application user will wonder what's going on.
With all that being said I have been looking into C# with Managed DirectX. I figure if I ever release anything it will only be run on a Windows OS so multiplatform isn't that big of a deal. Of course there is always Mono. I could always go back to C/C++ but for a independent developer there is far to much is to be gained from a higher level language of you can get the performance. If I ever run into performance issues I could always interop into a C/C++ DLL. I've already had to do this to get high performance timers.