This was a huge discussion on all the boards when it was released. I think the high ISO (1600 & up) have been improved. I never shoot above 800, so I've not noticed a difference in any of my shots.
I was hoping this software update would keep my CF door from sticking
I think it very odd if the firmware did improve high-iso,
or other issue and not have it put in the release.
I have not noticed any outisde improvments, but
I tend to stay away from high iso most of the time