So I just built my new PC (Athalon 64x2), but my GPU hasn't arrived yet. Just for fun, I fired up the Horde samples on the integrated 3300 HD GPU, and I was pretty surprised by the results: the knight sample maintains a steady 35 fps, chicago a steady 22, and the terrain sample 145.
I know the 3300 is the state of the art as far as integrated graphics, but still, I am impressed. Those are roughly the same frame rates as my last machine with the dedicated X1600 (although Apple's drivers may have been slowing it down).
Can't wait to see how it performs once I get the 4870 HD in there...