you are equating the nvidia blob to that of the ati driver when you say that every driver has some unavoidable bugs. Yes both drivers have countless bugs. One of these drivers is alot better then other other and i think its clear which one. By better, i mean lesser of these "bugs". If a driver cannot handle certain filters or shaders or whatever, it is lacking. The only barriers my nvidia cards have ever had with the proprietary driver, for my 3d use, is the gpu limitations itself. You can compare the performance of the nvidia blob against its windows counterpart but an ati linux vs windows is an absolute slaughter and you know it; particularly getting things running to begin with. On windows you dont need to touch your video driver utilities unless you are getting serious. I cant say i have ever needed to do it with either a nvidia or ati card under windows, even as a heavy gamer.

Let me just quote carmack here.

Yes, it is. The codebase is much, much larger, and the graphics technology pushes a lot of paths that are not usually optimized. It probably wouldn't be all that bad to get it running on the nvidia binary drivers, but the chance of it working correctly and acceptably anywhere else would be small. If you are restricted to it only working on the closed source drivers, you might as well boot into windows and get the fully tested and tuned experience...

John Carmack
Its not like hes joe blow, we can account some of our best games to some of his work. So he has a major voice. the ati driver is clearly one of the things holding up linux gaming. As steam, a game distribution company, this is a very big deal. Key is getting things going in the first place. I think he means it must be harder.