I upgraded my D7000 to a D7200. There was nothing really wrong with the D7000, but I was somehow never happy with it. Here are some reasons that made me upgrade
Non lockable command dial
This is easily the biggest reason that made me upgrade. I mostly shoot at aperture priority and I must have lost atleast a million shots just because that shooting mode shifted without me noticing. The lockable command dial is a big plus for me at least and I no longer have to worry about the shooing mode changing accidentally.
Presence of an AA filter
After owning the D800E, I have become a fan of its sharpness and crisp pictures that have a pop, that just could not be replicated by my D7000. I often saw that the micro feather detail was always a bit smeared on my D7000 compared to my D800E. I have seen enough samples on the internet to finally conclude that a non AA filter camera gives noticeably sharper results than a camera that has one. So another reason to upgrade.
Nikon has always dumbed down their enthusiastic cameras unlike Canon for some basic things like faster FPS a decent buffer. The D7100 is a classic example of this. It has a RAW buffer of only 6-7 shots with the fastest card available in the market. It had an excellent 24MP sensor with a 51 point pro AF used in some of the top Nikons, but with a 6 shot RAW buffer it was a joke. The D7000 had a better buffer. But there were many instances when I found that even its 11 shot buffer was inadequate. The D7200 had a much better buffer of around 18 shots and that clinched it for me. Its more than 27 with the 1.3X crop mode.
51 point AF with -3.0 EV AF point sensitivity
After using the D800E’s fabulous 51 point AF array the 39 point D7000 array was always lacking. Also the center point has a -3.0 EV sensitivity that will really be useful in early morning and late evening safaris. Early testing reveals that this really is a big upgrade and I can easily focus in extremely low light.
16 MPs same as my D800E in crop mode.
The DX crop mode on my D800E gave me the same 16 MP resolution as my D7000. So I really needed more pixels to crop and more pixels on my subjects (mostly birds) and IMHO 24 MP is plenty for the moment. The D7200 also has a handy 1.3 crop mode giving almost 14 MPs at 2X reach with all the 51 points covering the entire area of the 1.3 crop mode. I have a 200-500 5.6 on order that will give me a nice 200-1000mm birding/wild life kit that is hand holdable. I now see this combo along with the 70-200 F4 on my D800E as my primary safari kit.
Wi-fi and NFC
Though not absolutely necessary these are good to have for quick downloading of important images to my android smart phone.