Barring KK's posts, the entire discussion about how OpenGL was killed by Microsoft is completely lame. As KK mentioned, OpenGL was doomed from the beginning for games anyway. The basic reason for this was no one in the ARB actually thought games were a relevant application.
What DX did was create a standard to write games. DirectX is way more than just a plain 2D/3D rendering API. It had APIs for sound, media, networking, input etc. Some of them caught on while others were dumped because of lack of support from the game development community. OpenGL on the other hand was purely a graphics API leaving everything else to the programmer. Even OpenGL games like Quake and Doom use DirectX for other functions like input and sound.
Microsoft did not kill OpenGL. All it did was that it didn't update the default OpenGL software accelerated driver that comes with Windows. Not that it mattered anyway cos no one in his right mind would use a software rendered version of GL as its dog slow no matter what OS it is. In terms of Hardware accelerated GL, as KK mentioned, the capabilities were completely decided by what ICD (installable client driver) exists on the system based upon the graphics capabilities and this ICD is provided by the hardware vendor. Microsoft had little to do with it.
To tell the truth, OpenGL is no more "open" than D3D. The spec is available to everyone just like D3D but the original implementation is as closed as D3D. Infact SGI probably has more patents on various components of their implementation of GL than Microsoft has on D3D. This again is the reason why linux accelerated graphics drivers still remain closed source.
Yes OpenGL has open source implementations from ground up such as Mesa3D but again thats just a software renderer and it hardly is gonna be used for anything serious. They are as useful as the GDI Generic renderer in Windows.
As far as usage in Vista is concerned, the whole deal was misreported by some lamer and blown out of proportion. IHVs were free to develop their own ICDs that would work in Vista natively. The only catch was Aero could not function when the ICD is being used since aero is based upon D3D which needs exclusive access to graphics hardware just like OpenGL. The layer on top of D3D was actually a step forward compared to the implementation in XP as it was hardware accelerated using the default D3D driver unlike the dog slow software implementation in XP. Since this actually uses D3D underneath, Aero can work with this GL renderer.
Personally I prefer OpenGL to older versions of DX as it was pretty dirty at the outset. However DX10 is significantly cleaner and easier to code in as compared to 8 or 9 and i'd choose it over the mess that GL 2.0 is anyday.
