Geforce 8900 GTX has 25 per cent more shaders
 

Last year NVIDIA launched the 79xx series in March, an upgrade from the then high 78xx products. Now they're doing it again for the 8800 GTX:

"If Geforce 8900 turns out to be using the G80 chip, that will mean that the chip had more Shaders all along. Our sources confirm that Geforce 8900 GTX has more shaders. We know that this will speed up some of the games

http://www.theinquirer.net/default.aspx?article=37610

looks like NV moves in for the kill