I agree with Moryath. I owned a nvidia card and it really glitching bad everytime you start a game that require full 3D. i never had a problem with ATI card

They only support two OS: Windows and OSX, i played WOW on my MacBook Pro with OpenGL without a problem. Right now, many company can start supporting OSX since Apple went to Intel. Linux is not popular in gaming world because Linux is mostly used in servers. Company dont want to waste their money to hire a Linux Programmer to add support for game to work on Linux if Linux market is not big enough to meet their own requirement. But now they are adding support for Linux as well like Second Life, it still in alpha stage. For games to work on cross platform, you have to hire a programmer for specfic platform to make it work and it cost money for them to pay the programmer.