That Nikon has changed to feel and operating concept not too much compared to the D7000 (and other DSLRs the Nikon family), I find welcome. In general, the D7100 is not a revolution compared to the D7000. But many small changes and additional options add up to a noticeable improvement of the intrinsic values of the camera.
The video performance I have not tested for video I use the DSLR (not even to make phone calls, as apparently some other reviewers would like to do it ...). For continuous shooting performance, I can not say much also; in various forums, the design of the buffer memory is so criticized, but in my (admittedly undemanding) small series I could here no limitations noted.
A few statements that I can venture after three days:
The autofocus is noticeably improved, not only in terms of the number of measurement fields, but also the ways to use them flexibly, and the speed, especially in low light. The focus speed is of course also depends on the lens used. 50mm fixed focal length or medium range, for example, the 16-85-Nikon Zoom focuses faster than a stronger telephoto zoom but everything's alright. (Which I however prefer focusing manually) Incidentally, during macro shooting, for example, with the Sigma 150s.
The high-ISO performance seems improved over the already pretty good D7000. At least until 3200 ISO, the noise keeps in good limits and if at all, only in dark areas visible (at 100% size).
The viewfinder is perfect for me, not only the viewfinder image is brilliant, but also the information which / next present themselves clearly and very well cleaned.
The shutter sound (mirror shock) appears more muted, especially in Quiet Mode in direct comparison to my D7000.
The easy access to important functions via the i button and flexibly assignable other buttons offer additional ease of use; the possibilities of individual settings, however, were also in the D7000 already quite numerous.
The battery life (if you can say something after a few days) appears according to the charge level indicator is not from "consumption patterns" of departing D7000. I have an existing from the D7000, I know as a reliable battery EN-EL15 inserted, which in the first days of testing just acted like the D7000. Therefore, I start from a long term.
Any criticisms for D7100 I have not (yet) found. But I am also not spasmodically after ...