Eric, thanks for your informative post! Feather detail in birds is also one of my concerns, and a reason why I have not decided yet between the D800 and D800E.
With respect to Leica, I doubt that the lack of AA filter is the primary reason for the way Leica images look and their sharpness and contrast. I think the Leica lenses as well as the Kodak CCD sensor have more to do with it. Since there is no Leica with AA filter, we can't really determine the effect of the filter.