New PureVideo?
There's no other change between the G94 and the G92 - at least, not officially. The improvement in ROPs (a better compression ratio at high resolutions) Nvidia is touting was already present on the G92, and hasn't changed, like the improvement in texturing units (doubling the number of address processors per filter unit). The only addition is native DisplayPort support (the presence of the interface was left to the partners' discretion).
The same goes for PureVideo: the GeForce 9600 GT's implementation is strictly identical to that of the 8800 GT (PureVideo 2). On the other hand, new PureVideo HD functions have been added via the 174. drivers, which were made available to the press only for the 9600 GT. There are four improvements: dynamic enhancement of color and contrast (the exposure of each frame can be corrected via the histogram, meaning that it's calculated 30 times per second), simultaneous dual-stream video decoding (Picture In Picture is supported, though with new versions of the players), and finally the possibility of keeping the Aero interface when playing HD video.
In practice, we examined the differences using several films - we weren't able to make captures of HD films - and the only one we thought we could discern a difference in was Full Metal Jacket, Chapter 7, where the detail in the backlit shadows seemed a little better with the 174. drivers (due to the improved contrast). Even here, the difference didn't really jump out at you. That makes sense, since the masters for HD movies are especially carefully prepared, and unlike a TV signal, with HD there's not much that needs improvement.