I've been around cameras over 50 years, and got my first DSLR in 2010 (a Pentax K-x), but after a number of upgrades, and a few diversions, ended up as owner of then brand new D600, and what a revelation it is!
The D600 is just slightly heavier than my last Pentax, but a much more capable camera. The bigger sensor improves both image quality, and dynamic range, as by magic. Slightly more complex to operate than my old Pentax DSLRs (some of it due to me not being used to Nikon DSLRs, I suppose).
Amazingly good AF, good endurance (almost 1000 shots per charge).
In every way a nice camera, except for the quite common problem with dust/oil on the sensor had the same problem with my Pentax K-5, actually, and that was worse than my problem with the D600.
The replacement D610 fixed the shutter issue, and gave it an even quieter shutter mechanism!
D600 are available on the used market for around 1000, or about half the cost of the D610, giving the shopper an excellent choice, new or just slightly used/rebuilt.
It is a pure delight to use it with my new AF-S 80-400 VR II, even in very bad light.
