We have an English review from FPSLABS and we also have a translated Chinese review from PC Online. Looking at the English review, the only game that the X2 really did well in was Call of Juarez. The X2 did not do much better (and sometimes worse) than the other cards tested. The Chinese review tested more games but they only tested it versuses the 8800 Ultra. The X2 did better in Call of Juarez, Call of Duty 4, Need For Speed 11, Unreal Tournament 3, Serious Sam 2, and F.E.A.R.
Another English review is here but I can't view their snazzy animated charts here at work. :(