Correction: Rather than say that NVidia is in bed with Microsoft (with regards to the integration of GeForce 3 features with DirectX 8), it is probably more accurate to say that Microsoft is in bed with NVidia, and designed the DX 8 API around the new features on the chip. Microsoft, without question, had plenty of input as to what those features should be, but by all reports so did traditional OpenGL advocates such as John Carmack. More on that in a moment.
NVidia continues to expose its new features in the OpenGL API through well recognized OpenGL extensions. Many of these extensions will eventually become part of the OpenGL standard (for a clear instance of this look at the evolution of SGI_multitexture to ARB_multitexture) and in the meantime, other vendors are free to implement any of the NVidia features they deem worthy in either software or hardware (just as they are free to do the same for their DirectX 8 products).
Certainly NVidia has an awfully close relationship these days with Microsoft; they are providing not just the graphics engine for the XBox console but also the sound and system chipset (new directions for the company, as of this writing). But it is premature to suggest that because the features of the GF3 are well exposed in DX8 that NVidia is fleeing its roots as a solid supporter of OpenGL. John Carmack has publicly expressed his support for the chip, calling it a "must have" for developers. In fact, developers of all persuasions have generally hailed the GF3 as the most important advance in consumer 3d technology since the original 3dfx Voodoo. There has been little concern amongst that community that NVidia's OpenGL support would be sub-par or lag behind the DX 8 support.
The new NVidia OpenGL extensions include NV_evaluators, NV_vertex_program, and NV_texture_shader.