Folks, it's not that OpenGL itself is slower than DirectX, it's simply the fact that OpenGL has always been treated by the industry as the professional API for graphics workstations and DirectX was the API for games. So the high-end graphics cards have OpenGL-optimized drivers that will blow any DirectX driver out of the water. But when you enter the consumer market, the developers will have focused on DirectX and optimized their drivers only for that.
Enter Vista: OpenGL calls are now translated to Direct 3D calls, making it impossible that OpenGL on Vista will ever match the performance of Direct 3D. And that is not the fault of OpenGL, but of Microsoft's OpenGL implementation.
Anyway - if you ever want to support something other than the Microsoft platform, you should go down the OpenGL road and leave DirectX/Direct3D aside.
Enter Vista: OpenGL calls are now translated to Direct 3D calls, making it impossible that OpenGL on Vista will ever match the performance of Direct 3D. And that is not the fault of OpenGL, but of Microsoft's OpenGL implementation.
Anyway - if you ever want to support something other than the Microsoft platform, you should go down the OpenGL road and leave DirectX/Direct3D aside.