Because the preliminary benchmarks told us so?
Well the only benchmark I've seen was from a review on some Chinese site. I'm waiting to hear the whole story on these things from more reliable sources, as well as a subjective evaluation of what they're like compared to the core 2s, given the same clock speed.
Even if clock for clock they don't outperform core2's in games, I think a 3ghz q6600 will be squashed by a 3.2ghz i7 when that is overclocked. I can't imagine my TF2 framerates not benefiting... Or any other CPU limited game for that matter. I'm not comparing apples to apples, I'm comparing what I have now to what I would haave after a large expenditure of money.