The images look similar to those i've seen elsewhere, maybe a tad better. Certainly a far cry from my wifes G11 which she really likes. I've pre-ordered, I could use it this week, since I have some low light no flash theatrical photography coming up.
I usually use my 5D MK II at ISO 3200, and only a few at 6400 where I have no choice. LR 3 has improved those high ISO images enough that I might be happy with ISO 6400, but I still avoid it, detail is definitely missing. My 7D is limited to ISO 1600, maybe stretched to ISO 2000 in a emergency.
The printed images look fine at even high ISO, of course.