Nvidia drivers are not unstable. Unless being one year with drivers that never crashed means unstable, they are very stable if you know how to configure your X. And who cares if they don't do them free software? Ati isn't really better, they didn't even want to release their specs so that free software developpers could do drivers. ATI has a very low karma in my mind. NVidia are much better.
I agree that after I poked around the os-regstry.c things got better, the nVidia + via problem is really related to the AMD bug. It just gets worse using the nVidia drivers... Trust me on this one GnuVince (Why do you call yourself that when you do not believe in Free Software?)
ATI fonded the DRI development for a long time - but then they stopped doing that, they still release tech. specs. under NDA for the X developers - something which nVidia has never done.