New drivers are still making the FX series perform better.
I think, somehow by making the 6800 perform better in the driver, we get performance benefits too. It could be that nVidia is still working on improving the FX series? We do get a lot of the same IQ options as the 6800 (i.e. High Quality, Tri Opts, Aniso Opts, etc) which older cards simply don't have in the control panel.