I get about 50 fps with Mafia II, about 85 fps with Modern Warfare II, which is exactly the same as I used to get with the 5770. Physix is disabled, everything else on high.
Perhaps I was expecting an increase that just isn't there, but all of the benchmarks that I have seen show the GTX460 (768mb) outperforming the 5770 consistently. I would have gotten the 1g version but the 768 version was on sale for $166.
Thanks for the input thus far