I plan on doing video comparisons, but I'm working the stills side of things for the moment. It might be a couple of weeks yet. Some quick and dirty video clips that I've shoot look very nice.
Lloyd Chambers has done a comparison between the D800 and the Leica S2 and finds that it is somewhere between and raw and a slight win for the Nikon. The D800e will therefore likely win in almost all IQ counts.
The D800e is medium format's worst nightmare. Resolution matching cameras and backs up to 40MP, superior high ISO, equal colour depth, lighter weight, availability of hundreds of lenses, availability of stabilization, live view, video, much higher frame rates, and all for an integrated body costing less than US $3,300.
Since you've tested the Sigma SD1 as well do you feel that at low iso compared to the D800e, the Sigma is dead in the water from the aspect of pure image quality alone in prints 16x20 and under?