Large I/O memory in small address spaces

Look, you have to start somewhere. It's not like linux <2.6 (or <2.6.10?) was that great for all kinds of workloads, and it certainly took quite a bit of work fixing it in the 2.5 and 2.6 series.

Nobody has really worked on graphics in the same way. This is just the beginning, besides hardware does not provide a generic interface such as the intel and amd hardware does. So it's not that easy.

Also, I'm sure nvidia has quite a bit of resources to throw at their driver. They even have time to hardcode (like rewriting shader x if game y). That is just insane from resource perspective.