HEXUS compare some Crossfire benchmarks they snagged at Computex with some benchmarks from other cards on a similarly-specced system.

Using Supertiling, the default mode for Crossfire under Direct3D, shows that 6800 Ultra SLI is faster. However that's just in 3DMark05, not a modern game title, and that's using a beta driver that might not be there in terms of the performance that ATI have today, internally. It'll be interesting to see where performance is when Crossfire is launched using an official driver, along with NVIDIA hardware running any new driver that NVIDIA may or may not have planned for their hardware.

ATI Crossfire Sneak Peak with DFI