3D Mark
We can see that the 6800GS comes very close to the Ultra in all tests, especially when overclocked, the "missing" pipeline doesn't show to be much of a disadvantage.
Aquamark 3
Overclocking seems to have done wonders in these benchmarks. The OCed card comes very close to its brother when anti-aliasing and anisotropic filtering is turned off. When the test is run with 4xAA and 16xAF, the overclocked 6800GS has a 1050 point lead over the Ultra.