NVIDIA GeForce 8600: Full H.264 Decode Acceleration
 

Although we haven't been terribly impressed with the gaming performance of the GeForce 8600, it is currently the best option for anyone looking to watch Blu-ray or HD-DVD on their PCs. The full H.264 offload onto the GPU makes HD movie playback not only painless but also possible on lower speed systems.

http://www.anandtech.com/video/showdoc.aspx?i=2977&p=1

Surprisingly good results, 8600 is better than 8800 for H.264