I'll say that 3DFX was a bit odd with their driver support, being an old school and proud 3DFX owner here. Damn their drivers were buggy - but when they worked, they worked like a charm.
3DFX never needed to impliment an OpenGL driver for their cards, as their Glide API could process all the commands used in OGL. Difference being, though, that the Glide API only made use of the commands useful for gaming, so it wasn't nearly as bloated, but, it was extensively faster at the time than any other competitors when rendering OGL based applications - and taking into account this was back during the time that DirectX and OpenGL were first gaining momentum, also, it helped push the VooDoo cards to the performance throne.
True, the VooDoo cards were 16bit dithered, but the cards were still capable of near 24-bit output, and still
technically rendered a 32-bit image. The actual display output was hard to distinguish any real color differences between a VooDoo and a competitors card; if you happened to own any of the VooDoo lineup, you should be able to remember that. The big difference that everyone pointed out, though, was in their screenshots.
3DFX was a hardware company that carved their niche for performance graphics in gaming, and that led to their downfall (amoung other things). They became complacent after the release of the VooDoo3 (which, IMO, was their best card they ever offered), and towards the end were releasing a bunch of insane products to try and recapture market share (one of my favorite 3DFX marketing slogans was "So Powerful, it's kind of ridiculous") - multi GPU cards (there was a card planned with 4 GPUs, required it's own power adapter, but never released), multi SLI setups (4 card SLI was possible, I think they might have even offered a 5 card setup, too). Still, though, they were a pivital company through the late 90s, and I really think they paved the way for strong 3D graphics support and performance. Love 'em or hate 'em, they had a lasting impact on the PC market, and will always be revered and remembered by both the die hard fans, and tech junkies alike.
You might find this an interesting read:
http://www.x86-secret.com/articles/divers/v5-6000/v56kgb-1.htm