>All I know of the difference is the claim that the D800e is >'Optimized' for shooting NEF format.
That's a dramatic oversimplification. Basically the E has an anti-aliasing filter which cancels its own effect, as opposed to the D800 which has a traditional anti-aliasing filter.
The anti-aliasing filter's job is to blur details which occur at about the frequency of the sensor's pixel pitch, which is to say, the smallest level of detail the sensor is capable of recording. The purpose of the filter is to prevent unnatural moiré patterns from occurring in fine-grained repeating patterns like fabric or window screens.
As you might imagine, images from the E should be sharper out of camera, with a risk of moiré. It's debatable whether the additional detail recorded by the E is even real, or if the D800's files can't recover to a similar level of sharpness through post-processing.
My take, if you're shooting things with fabrics or architecture, get the D800. If you're shooting things like landscapes, then you might consider the E.
Here's the ongoing thread discussing these issues: