In every professional review all they really say is that G92 = budget G80 with ROP partitions sawed off and bandwidth tightened up to save on the manufacturing costs, plus slightly optimized shader processing algorithms and similar to make up for the drop in ROP count to some extent, with some HD-decoding and media stuff tacked on, hence the increased transistor count.
After lot of searching and going through 1000s of posts on various forums and reading many reviews I have come to the conclusion that clock for clock there is not much difference between G80 and G92 cards, if any, except G92 cards run cooler and therefore can be clocked higher and that G80 cards, especially the ones with huge amounts of VRAM like 640MB GTS or 768MB GTX perform up to 100% faster in high resolution AA/AF situations due to their wider bus. (320bit/384bit on G80 vs 256bit on G92)
I found an informative thread (link below) on this German forum last night where a guy compared a (G80) 8800GTS 640MB to a 8800GT 512MB both with severe and nearly identical overclocks. (both 700Mhz+ on the core) and in high resolutions with AA/AF pumped up GT performed 100% slower. 10fps vs. 20fps. I've run into similar information in professional reviews where reviewers used higher resolutions, or mid to high resolutions with AA/AF pumped up.
Also, when AA/AF are off and when G80 and G92 cards are clocked identically then they perform pretty much identically as well. This guy @ ocforums (link below) clocked his 8800GTS 640MB to same clocks (core\\shader\\VRAM) as OC an version of 8800GT 512MB and he got identical results in games and benchmarks. (with AA/AF off)
Popularity of 8800GT = Marketing hype? After spending days reading random posts and literally dozens of reviews, in my opinion, to some extent I think so, yes. Little bit of fanboyims as well I think. I think G92 finally allowed many people to have G80 performance or better (stock to stock) without having to sell their kidneys to be able to buy a G80 card. And the people who dumped their G80 cards? Victims of hype and marketing or just one of the “I gots to have the latest even if its not better cuz my neighbor got one” type of people.
I for one will be SLI-ing two 8800GTS 640 cards since I will upgrading my monitor and I intend to play at high res with AA/AF.
I guess I answered my own question there, although it took many hours with Google.