.. despite having native ISO 6400, plus an "H" mode of 12800, it isn't really that much better for noise than the 40D was (native 1600, "H" of 3200).
The 7D here seems to be somewhere between 1 - 1.5 stops better than the 40D, though the built-in noise reduction firmware makes it hard to tell.
Time to amend that thought: Having now seen some of the images (at reduced size) on my 1920x1200 IPS notebook screen, I'd say the 7D is giving me at least 2 stops extra for usable ISO, over the 40D. Which is pretty good considering the 40D was widely thought to be less noisy than the 50D, and the 7D is reported to be only slightly better for noise than the 50D.
Maybe it's the built-in noise reduction, maybe just the binning of pixels when images are reduced for display.. dunno, but the ISO 3200 / 6400 shots look fantastic!
Cheers