Just upgraded to 3770k. Usage of CPU in BF3 is not max 50-60% so yeah, HT helps a lot.
Still no sure about performance of Crossfire setup. The usage spikes between 70-95%.
I agree I am currently still using my i7 920 at 4Ghz with HT I'm at 60-70%, and with HT off I sit at about 85-95% and my frame rate seems to drop by 5-10 frames on average.
I would say if you can OC to 4.5 Ghz you would see a pretty good performance gain.