I have to admit that I have a single ATI 4850 and it was a real pain. Once it was setup and working, I than had some black screen and losing all possibilities to change anything because the console was to the black screen.... anyways it wasn't that simple because on some other OS you simply need to go in the Screen configuration and that's it. In Ubuntu the Screen configuration had only 1 of my 2 screens. So... I guess it's not up to the simplest it can be.