The benchmarks are only at 1280X1024, and they don't say anything about AA or AF levels, but they're numbers to look at, nonetheless. The XT version of the R600 seems to certainly hold its own against the 8800GTS from what these numbers say.

"AMD pairs the R600 GPU with 512MB of GDDR3 memory clocked at 1.65 GHz across an eight-channel, 512-bit memory interface. In comparison, the NVIDIA GeForce 8800 GTS features 640MB of 1.6 GHz GDDR3 memory on a 320-bit memory interface."