A well-tuned low pass filter does not really lose any detail, whereas a camera without a low pass filter will generate false detail. A filterless camera is destructive to detail.
Now I'm confused
What would be the advantage of having a different version of the D800 without a low pass/AA filter then? I somehow gained the impression that it was for e.g. landscape photographers who want more detail in their images. If absence of a filter generates false detail/is destructive to detail, what would be the advantage of leaving the filter off?
Low-pass filtration is a bit of a controversial topic. It boils down to spatial frequencies (wavelets in two dimensions), and how they are recorded. When you have spatial frequencies smaller than the nyquist frequency of the sensor (that really just means three rows of pixels are necessary to resolve one "cycle" of spatial frequencies, a ratio of 1.5 pixel rows to line pairs), the effect those frequencies have on image detail is largely indeterministic. The general result is that at very fine levels of detail, noise and aliasing increases. The intent of adding a low-pass filter is to blur spatial frequencies that are smaller than the size of a pixel, while simultaneously leaving spatial frequencies as large or larger than a pixel unaffected. Designing a perfect low-pass filter can be difficult. You don't want to design it too strong such that it blurs useful frequencies, however you don't want to design it too weak such that it doesn't blur enough non-useful frequencies that you still get noise and aliasing.
When it comes to landscape photography, the random nature of detail mitigates the impact these "useless" spatial frequencies impose when they are recorded by the sensor, which is why its not really a big deal to eliminate the low-pass filter for such photography. However when you have fine detail in repeated patterns...such as with fabric, the impact those "useless" spatial frequencies impose tends to result in semi-random coloration...color moire and concentric color banding or color sparkle. That is as much a consequence of using bayer-type sensors as it is due to the removal of the low-pass filter, though. With a Foveon-type or monochrome sensor, the effects of not having a low-pass filter are FAR less. The original Foveon sensors did not actually use a low-pass filter, if memory serves, and it was only in the more recent generations were low-pass filters added.