I am going to guess that this camera will be very popular in Japan and China, the latter where there is a new infatuation with classic glass. I understand that, I've been infatuated with classic glass for 20 years now. The camera can use and meter with pre-AI lenses, the first Nikon DSLR made to do so. The camera even has an "uncoupled meter mode" which has not been seen since the Nikon Tn meter of 1967 or so.
As for more "bells and whistles" than the user of a Nikon FE2 or F3HP would like to see- most people are used to them. Nikon's competition will be the new full-frame Sony mirrorless camera, used with an F-Mount adapter. That means using the aperture manually, a dark viewfinder at F5.6 or so, and manual focus for all lenses. The Df- I can use with pre-AI lenses, set an Aperture on the lens and dial into the camera, use on aperture preferred auto and focus with the lens wide-open. Better than using with a Sony. I can use a Nikkor AF lens on auto-everything with the Nikon, not so on the Sony.
We'll see what the prices of older Nikon glass do with this new camera. They are already way up from a few years ago because of mirrorless cameras. Prices of used Leica glass where cheap before the leica M8 came out. $70 Summicron, $70 Canon 50/1.5, $95 Nikkor 5cm F1.4, etc 50 times over for me. I paid for a Leica M9 and M Monochrom by selling off lenses and still have 60 of them in Leica mount. I have at least 100 lenses in F-Mount. $25 50/1.4, $25 55/3.5, $50 5.8cm F1.4, $125 55/1.2, etc.... So- back to the build quality on this camera. If the lens mount is screwed into plastic as it is on the D600, that would stop me from buying it. I'm guessing it's closer to the D800, Nikon still remembers that their old lenses were heavy.
Just to add- prices of Nikkor lenses in Leica mount- way up, about 6x in the last 10 years.