I was always an NVidia kinda guy but my current beast of a desktop has an ATI card, a 2900HD pro, which has been good to me. i've barely noticed any problems in games and such, terragen wise its always been good to me. Generally if i hit an issue in a game, a simple driver update fixes it. Though there was once where I updated my drivers, they had a bug in them where the top left pixel of your screen was always white, which annoyed me so i had to downgrade for a month or so until i checked again. They do update their drivers often though.