I must at least partially disagree with some of the comments above. I own BOTH the S2 and the D800E.
(1) With Leica lenses, the S2 images are superior in resolution, MICRO contrast, tonal range than the D800E.
The images have a three dimensionality that I cannot achieve WITH NIKON LENSES on the D800E.
(2) On the other hand, fitting Leica R lenses to the D800E achieves close to if not the same effect. So, a lot of
what I see is the glass.
Note that I do my comparison in PRINTS (minimum size 12x18, typical size 20x30 and often 40x60) as well as the screen.
That said, the points regarding autofocus and frame rate are important and favor the D800E (if you do not have
the left focus issue).
I often find myself "tweaking" the auto focus of the S2. However, the viewfinder on the S2 is so bright, so large
that it is as if I am not looking through a camera! The D800E does not begin to approach this experience. Couple that
with the microprism focus screen on the S2 and manual focus is as fast and more accurate (don't need to move a small
box around the view).
But, I believe the most important factor in this decision is how you photograph or what you are trying to photograph
or achieve. Clearly, if it is animals in motion (or sports) then D800E is definitely a more appropriate camera.
If, on the other hand, you prefer either animal "portraits", or especially "environmental" nature photography, then
the S2 is probably more appropriate.
Also remember, that if you want to use very long telephotos (400mm, 600mm etc) then you must go with the Nikon.
What I find is that the type of images I take are different with the S2 than with the Nikon. My approach to the subject
This can obviously be an advantage or disadvantage; I often find that it makes my images different and forces me to
be more creative. That part is good.
Incidentally, if you want to see some "wildlife" images from a S2 and the 120mm lens, please visit my websitewww.rudlinfineart.com
and go to the butterflies under the galleries->portfolios menu.
Which ever system you get, you will not be disappointed. They are just different.
But, if you go with the Nikon, do take a few Zeiss or adapted Leica-R lenses. Even though they will be manual focus
you will see the difference in the images, especially if printed reasonably large.