though the photo quality is awesome.
Please never post Nikon iso comparison shots on a Canon site again, Nkon's iso1600=iso100 and Nikon's iso3200 equaling Canon's aps-c iso100 will increase suicide rates of Canon owners so much there won't be people left to buy the 6d. Not that there would be many to begin with.
Looking over the Imaging Resource test images, the D600 at 3200 looks a lot like the 7D at 1600. There's greater separation at 3200 and 6400...just like with 7D/5D comparisons...but no great difference in any respect at lower ISOs...also just like 7D/5D comparisons. I can confidently say that I could make two 24" ISO 400 prints from the 7D and the D600 and you would never know which was which.
And the 5D3 looks better at 6400 than the D600 at 3200. That surprised me, but it's a pretty clear difference in favor of the 5D3.
The small edge that Sony made sensors generally have in shadow and high ISO noise has been blown way out of proportion by Nikon fans and turned into an online myth. Much like how FF fans will swear on their mother's lives that there is a huge...just HUGE...difference in IQ against crop sensors even though they can never confidently pick between unlabeled samples and prints.
It's human nature I guess.
As to the 6D...the problem is that it has been stripped down way too much for the price. The 5D3 is a great camera, but should be priced between the D600 and D800, closer to the D600, but a bit more. The 6D should be priced well below the D600, and even then should not have been stripped down like it was. And I fear Canon's 46 MP beast will be sold at a beast of a price, more than the 1Dx.
Part of the reason I went with Canon a decade ago is because Nikon stripped down their lower end bodies to the bone, thought way too much of themselves, and priced accordingly. Now Canon seems to have that attitude, while Nikon wants to be cut throat competitive. I don't like what I'm seeing in terms of Canon pricing for a given feature set.