I have been to a Nikon NPS event here in the Netherlands were several comparison shots D800 vs D800E were shown. These shots were not printed though, but presented via a projector ...... so much for a projector, but alas.
The increase in detail/sharpness is there and indeed small, as is the increase in clarity. But what struck me was the increase in depth of the D800E shots - a more three dimensional look .... it is to be seen at the very first glance at the image and quite attractive. Hadn't expected this at all. The difference in depth won't knock your socks off, but is much more noticeable than the difference in sharpness between the D800 and the D800E.
I can quite well believe that, when both images have received the same processing. One would expect the D800E to have slightly better micro-contrast, that is, slightly greater contrast of fine detail and edges.
Really large images, such as those from a projector, tend to look better, more 3-dimensional if you like, when local contrast has been enhanced or exaggerated. The processing one might apply to an image to be printed at A3 or A2 size would not be ideal for a 4ftx6ft print or an even larger image from a video projector.
The question is, can one isolate and define the qualities in the D800E image which are responsible for that sense of greater 3-dimensionality, then reproduce the same, or very similar effect in the D800 image through different or additional processing, such as greater detail enhancement and greater clarity adjustments in ACR and/or greater 'local contrast enhancement' in PS and different settings in Photoshop's 'Smart Sharpen' etc etc?
Mind you, there is something to be said for getting a particular desired effect straight out of the camera without a lot of stuffing around in post-processing.