There’s been a lot said about the new Nikon D800 and it’s twin, the D800E. There’s nothing but a single letter on the outside to tell them apart and not much on the inside, either, with only the anti-aliasing filter cancelled out.
What does an anti-aliasing filter do? It (nearly) eliminates the effect of “moire” patterns caused by fine, repeating detail. See the Wikipedia article for more information. The cost of such a filter is that the resolution is decreased somewhat because the light is “blurred” (high-frequency component is removed) so that it hits more than a single pixel.
What this means is that the D800E without the AA filter will be able to produce an image with more detail than it’s brother. However, any fine, repeating patterns will likely cause weird color artifacts. If you’re a nature photographer, such patterns are not common but if you’re going to be photographing anything man-made (including clothes), the lack of an AA filter is going to create problems, problems that are very difficult to remove in post-processing.
I’ve ordered a D800 (no-E) for myself because experience has taught me that too much stress on the best possible performance usually comes back to bite you in many other ways. Better to have something that works really well in all situations than something that works perfectly in only a few.