I have only read a few of the posts in this thread. This is what I have to share. My partner and I have a photo studio in L.A. and we have had working relations with both Nikon and Canon. I shot for almost 20 years exclusively on Nikon and my partner on a Canon for almost 10. We have been shooting for the last 3 years on a 5D2. When the D800 and 5D3 was announced a few months back, we scoured the net for every review and user feedback there is, almost nightly.
We literally spend a few hours every day talking about this subject because we know that the camera we choose will be what we live with for the next three years and perhaps longer because it is a pain to switch. The feedback from the net about a D800 including DXO had my partner switch his entire system to Nikon, to two D700's and Nikons top glass, to buy him time until he could get his hands on D800's.
I could not wait to switch, being a Nikon fan boy but i decided to be prudent and just wait until after I did a side by side test of both cameras, D800 to 5D3.
Finally, last week we found two places that had both cameras available for us to shoot with. My partner was so excited because he was well prepared with all his beautiful Nikon glass and I was so excited just because I was used to my Nikon ergonomics. I know it sounds funny but I just never settled into the way the Canon feels in my hand and I often have to ask him to remind me how to adjust settings because they are not yet intuitive to me with Canon. I can pick up a Nikon and dial it in with my eye's closed.
Well, if you are wondering why the hell I am telling the internet all this in a Canon forum??? Well, I thought you Canon folk would like to know this. My partner and I live and support our families from photography. We are good at what we do. We took a D800 and a 5D3, with their best equivalent glass and shot them side by side, with the same settings. We did this for three days at two separate locations that had different cameras, just to make sure, there was no problem with any of the cameras influencing the outcome or the ambiance of the space affecting the color balance.
Moral of the story..... My partner has already begun selling ALL his Nikon gear. I am not switching back to Nikon...
Let it be known that when virtually every comparative shot was put side by side, the Canon won in sharpness, color balance or just a feeling that would draw us to the Canon image. The Canon shot was picked over the Nikon almost every time even though it was the smaller image and that size seems to usually impress / influence, as it would when we would compare a D700 file to a 5D2.
Moral of the story, no internet review or forum told us what our tests revealed to us, not one... Or if they did, they got shuffled because our minds seem to selectively choose what we want to read / listen to.. :-)
All the best...