The open ATI drivers really are improving. From my own experience, my home desktop with an nVidia 8800GTS can run for about a week before the display starts getting crazy amounts of corruption, and KDE grinds to a halt. My work machine, with an AMD HD4650 card, runs smoothly and never has any issues. Support for KMS is also a plus. I don't really do much 3D stuff on either machine though, so I haven't been noticing nVidia's generally superior OpenGL support for a while. Both machines have dual 1900x1080 monitors, and the home machine is a lot beefier than the work one.