Except for bugs and some lacking features, nVidia really does offer good enterprise quality drivers, and this is good for us desktop users (including gamers) as well. The performance is on par with the Windows drivers, and we need to remember the Windows drivers are far from bug free as well. If nVidia start focusing on the desktop as well, I think their drivers would quickly become even better.
What did nVidia screw up with OpenGL on GeForce 4xx+? My MSI N580GTX TwinFrozr II/OC works very well in Ubuntu 10.10 with 260.19.44, 260.19.06 did however create some interesting "effects" during load. Compared to fglrx, developing with nVidia drivers works very well, even though some driver versions have annoying bugs.