Q2 runs very nicely in GL on many many machines, emulating when it has to and amazingly keeping a decent framerate. It is very simple graphically, very basic in functionality, but a standing example of why John Carmack's well known speech on the subject of OpenGL vs D3D applies only to John Carmack and those willing to approach the API in the same way.
OpenGL is poorly supported, or not supported, by MANY video cards, even in current OEM systems. Yet Quake 2 will run at playable speeds using practically any of them, and a dated processor, with emulated (software) enhancements. EVERY patch to the GL renderer I have seen yet from the community thus far BREAKS IT on MANY system configurations. A lot of supposed "professional OpenGL programmers" who criticize Mr. Carmack's approach are responsible for OpenGL implementations that DO NOT RUN AT ALL, HAVE MAJOR GRAPHICAL PROBLEMS and/or CAUSE OTHER SERIOUS PROBLEMS on many many system configurations.
If for no other purpose these source releases should serve as an example, especially to those who hang on every word the man speaks, of what Mr. Carmack intended by his support of the OpenGL API. Q3A also has unprecedented support for a broad range of hardware, likely using similar methods of emulation, though the processing requirements rise respectively.
I hope this post gets read by a few people, and that at least one decent programmer takes it to heart. Alas, it will more likely only generate flames.