Hi, I'm a Nikon user, but I'm posting this here because most of the threads on D3 sample images actually seem to be posted in this forum. Personally I think it's pretty silly to make any comparisons between a few sample images, some of which seem to be from the D3, and some of which seem to be faked, and images from final production cameras that people on the forum actually own. Also, comments like "glad I didn't switch" also seem misplaced when the cameras aren't even on the market yet.
Before I make any serious judgment on the high ISO performance of these cameras, I'm going to have to see direct side by side comparison images taken in the same lighting conditions, with the same settings, preferably taken by me, in RAW of course. Also, I'd want to see printed images, why? Well, I sell prints, I don't sell web sized samples, and noise doesn't show up the same way in prints.
Speaking of noise, a lot of people talk as if lack of noise is the only measure of how "good" a high ISO image is. For me, maintaining color saturation and color fidelity is just as important, if not more important, a noiseless image will still look terrible if these two things are lacking. Even my D200 has great color fidelity at ISO 1600, which is still completely usable for 8x10 prints.
These are just my thoughts, as someone who won't buy a camera until I've actually handled and used it. I haven't put in any pre-orders for either Nikon bodies, I also know that even a 1D Mark II or 5D will blow away my D200 and D2X at high ISO, but I chose the Nikon bodies for different reasons, lens selection being one of them. Let's save some of the image quality judgments for when we can actually do apples to apples comparisons.