So how about the GTX vs. GTS (649)? the price difference is even bigger and the performace improvement even smaller?
I've never owned an 8800GTS so I can't tell you the actual visual difference while playing a game, but specifications wise they are different cards even aside from memory size. The GTX has higher clock speeds on the core and on memory, more stream processors, and larger memory interface. If you are running a higher resolution, like 1920x1200, then the GTX is definately worth it imo. Heck, even at 1680x1050 I have no regrets about spending the extra money on the 8800GTX.