It is not a big improvement... I don't understand nVidia's thought process on this one. ATI's R520 thought process is clear as day...
"ATI R520 is expected to be released on July 26th and will be built on a 90nm process. The R520 core is expected to based on an entirely new core design featuring SM3 (and above), GDDR4 memory support for memory speeds of 1.2Ghz+ and built in H.264 hardware decode assistance - the encoding standard for both BluRay and HD-DVD. H.264 decoding requires significant processing - a 3.6Ghz P4 runs at around 90 - 95% CPU usage without acceleration, compared to around 33% with R520 GPU acceleration. The architecture of the R520 is expected to contain separate pixel and vertex shaders (unlike the R500 core designed for the X-Box 360 which has unified shaders) with an expected 24+ pixel pipelines and up to 10 vertex shaders. The core of R520 is expected to contain well over 300 million transistors and will be available exclusively on PCI Express in conjunction with 512MB of memory. It is expected to retain at over $600 upon release."
XS RULES!!! I have officially referred you.