Well, I saw even the 8800GTX go down to less than 10 fps in Morrowind in some review so I would not be surprised if some people overestimate the power of newer cards and the 7600GT is a midrange card, my own 7950GT is more capable but it doesn't do wonders, the only thing crippling it a bit may be the 4x PCIe but some review concluded that the framerate hit of that is about 6% so I can only really tell once I have upgraded my mainboard.
I'd say never expect too much of a new graphicscard, try to expect a slight increase and then enjoy it if it gives more.