I never will either!Though I'll never forgive ATI for writing Catalyst Control Center in .NET...
But still... the ATi issues may have been caused by the graphics bridge on the system board. I just make sure that they both match... ATi using an ATi card and nVidia using etc.
I haven't had issues with either.
In some of the games I wrote in 3D unless the texture was a perfect square and not more than 512X512 (this was about 3 years ago) The .X objects I created would show as just white untextured models on most nVidia.
I couldn't market the games if that happened so WaHoo and HEXthello languished.
Thats another reason I switched to PB. I was getting tired of how BB3D handled the issues.

But still... nVidia vs ATi... I would say I support AMD and ATi. I am running an Athlon 64 3200+ on my rig and have had no problems with anything other than Quicktime... and the problem with that was burning it off the Hard Drive so it would not come back!!!