I wouldn't be so quick to jump to this conclusion... PCI Express is certainly more than just "AGP 16x". The fast GPU->CPU transfers could open up some interesting new possibilities for game developers, like offloading collision detection, physics calculations, etc. to the GPU to do load balancing. It probably will have minimal impact on existing games, but this could present more performance optimization opportunities for future games regardless of how much memory is on the graphics card. The more programmable and powerful GPUs become, the more beneficial this could become.