I've seen the results from the 800E, and they are stunning in terms of detail out-of-camera. For nature photography, you don't really need an AA filter.What's the point in a camera which can produce (in your eyes) better pictures in one particular scenario, while other scenarios are plagued by a design flaw?
Also, what about any nature shots with repeating patterns around the sampling frequency? Uniform vegetation such as some grasses or leaves, bird feathers, animal hair etc?
What you gain is false information. False sharpness. False detail.
Low pass filters are used in all forms of sampling to avoid aliasing. Aliasing is nothing but artefacts. If you can't excite aliasing due to oversampling, there is no gain to be made by avoiding a low pass filter.
Computers have for some time used anti aliasing to improve the percieved resolution of displays - this avoid the jagged edges, false details and create more realistic renderings.