Maybe, but in the far more useful sensitivities up to 1600, there is no way the D700 is going to match the detail of the A900, which gives a huge amount of headroom for noise reduction on your computer later. 1600 with one of those fast lenses (and anti-shake built in) is going to work in any sane amount of light, even without a tripod. And we haven't even seen what you can get out of the RAW files yet. I'd respectfully have to argue that it's looking very good for the A900 - until we see what the 5DII comes up with!
Agreed! At lower ISOs the A900 will deliver greater detail, otherwise there'd hardly be any reason for buying it. Clearly, these sorts of issues depend on your usage. Most folks will attempt to use the lowest ISO possible, consistent with a shutter speed that is fast enough for a sharp image.
But there is a dilemma here, when you know (if this proves to be the case) that image quality definitely suffers at high ISO, but also suffers at low ISO due to a shutter speed which may be too slow for the movement of the subject, if not for the movement of the camera. One is sort of caught between a rock and a hard place.
The dpreview comparisons indicate to me, if one is in a situation where ISO 6400 (and possibly even ISO 3200) is required for a sufficiently fast shutter speed, the D700 will deliver better image quality than the A900, period.
When the subject is moving quickly (a croc or a whale jumping out of the water, a footballer jumping for the ball), image stabilisation and/or tripod doesn't help much.
Speaking for myself, I want as far as possible a general camera which is adequate in all situations. I don't want to carry a D700 and at least one Nikkor lens for high ISO performance; another camera for best detail at low ISO, and yet a 3rd, cropped format camera, as a lens extender for my longest telephoto.
I would prefer a 39mp Canon full frame with image quality at least equal to that of the D700 at ISO 6400 (viewing equal size prints), and which has sufficient pixel density to make my 50D redundant as a lens extender. In the meantime, I'll probably settle for a 5D MkII. When its ISO 6400 images are downsized to 12mp, I wouldn't be surprised if image quality is on a par with that of the D700 at ISO 6400.