According to Nikon Rumors, the D800 will come in two flavors. We can only guess that they may be optimized along the lines of the D3x and D3s. That is, one will pack as many pixels as possible (36.3 megapixels) and be the choice for studio and lanscape, while the other will give superior low light capabilities (50-25,600 ISO) and outstanding dynamic range for amazing sports and wildlife photography.
One possibility is a model without an anti-aliasing filter. Most consumer digital cameras feature an optical filter in front of the image sensor. Anti-aliasing filters reduce sharpness, but remove color artifacts (jagged edges) and Morie patterns. Some image sensors, such as the Sigma Foveon 3X, have three separate layers (one for each color) and eliminate the need for an anti-aliasing filter.