So far from the benches, yes the 9800GX2 significantly outperforms the 3870X2. The gap may narrow a bit with driver updates from ATI, but I don't think it will narrow very much.
so i guess for sure the 9800 GX2 beats the HD 3870 x2? Its not that much in some games but in most games the HD 3870 x2 just blows, stupid drivers. Good thing im selling mine n waiting for the HD 4870 x2 that is right around the corner of Q2 2008.