As opposed to installing my nVidia fanboy friend's rigs (mostly 9800's and GTX series) and other friends who were willing to try AMD, I've had less problems with current Gen AMD's as opposed to the original one's which I must say were remotely bad. You are right though, I haven't owned an nVidia card, and I don't plan to either, I think my HD 3850 512MB is quite sufficient and all my rants about wanting more GPU power is just for GTA IV.
My worst luck with nVidia's drivers was their SLI support and dealing with nVidia chipset drivers. However, this is just my experiences, but 7/8 problems is still pretty bad; but I am an unlucky person.
With AMD's side, I did have a bit of trouble with the HD 2900's (way worse than nVidia's luck), but the drivers did improve with time though. No problems with the HD 3850 of mine, but I did have a fair share of bad luck with my friend's HD 3870 and HD 3850 CFX mode... I think he ended up selling those and just got an HD 4800, which he has had no bad luck with, as have with my other friends. Zmatt hasn't had any bad luck at all with his dual HD 4850's but I think Drizzt5 has been having some crap luck with dual HD 4850's.
I'm not saying nVidia are bad in drivers, just currently, AMD's winning both the war and the driver support. In the past I would have said nVidia won hands down.
(But I am comparing GTX's and HD 4000's when I mean currently though)