OK I think I've finally figured out the technique that I need to use for SHARP shots that the 7100 is capable of. The detail this camera can capture is amazing. . . but first your technique must be polished a bit and that starts with dialing in your lens. Surprisingly even manual focus lenses like my 500P can be fined tuned by tuning to the focus confirmation indicator dot visible in the viewfinder. Here's a link: http://www.youtube.com/watch?feature=player_embedded&v=7zE50jCUPhM
Once accomplished a manual focus lens can be almost as accurate as an AF one by merely following the indicator light and directional arrows in the viewfinder.
I took this capture at my cabin at a distance of about 30 feet and the lighting was dim to say the least. I used the 1.3 crop factor on the 7100 and this is about full frame. Oh yeah, this higher ISO capability of the D7100 is pretty awesome also!
Nikon D7100, Aperture Priority, ISO 1250, 1/160 sec., 1.3 crop factor, +.33 EV, Nikkor 500mm P manual focus (with crop factor=1000mm) @ f / 7.1, Induro AT413 tripod and BHD-3 ball head.