Shwow. I think my next rig will be a crossfire setup indeed. Either that, or I upgrade to a new mobo (perhaps x38?) and buy a pair of 3870's this summer.
But that's just incredible, in a lot of the tests it got close to 100% increase in performance, and like you said, there was one where it got over 100% (1600 x 1200 4xAA 16xAF).