Interesting and informative read, its amazing how the 2900xt is actually out performing an ultra at some resolutions and the GTS just cant compete with it.
http://www.anandtech.com/video/showdoc.aspx?i=3127&p=8

Also intriguing is the fact that the high end NVIDIA hardware seems to become CPU limited at less than 1600x1200. This leads to the fact that AMD's Radeon HD 2900 XT actually outperforms the 8800 Ultra at 1280x1024.
http://www.anandtech.com/video/showdoc.aspx?i=3127&p=8