I love the banter between comparing the new Nikons and Canon DSLR bodies. It reminds me of the Mac vs PC, Mac OSX vs Windows conversations.
A very important point that seems to never get mentioned in all of the articles comparing the Nikon D800 and Canon 5D Mark III is the fact that it can takes years and lots of $$$ to build a collection of branded lens and accessories. Personally, I've been using Canon cameras since high school and I'm going to my 40th reunion next year. Currently, I have the new 5D Mark III, the 1Ds Mark III, and a bunch of Canon L lenses and Zeiss 21, 50 and 100mm fixed lenses. Changing brands would be a very expensive proposition. More than likely, by the time I completed the conversion, Canon will come out with a new DSLR body that tops the Nikon and I will have regretted making the change.
There's no doubt that the Nikon D800 is an exciting advancement in sensor resolution and dynamic range, however, my friends, family and clients love my photos now and I don't think that they wouldn't appreciate the difference in camera bodies anyway.