Had the camera now for a few weeks - my other 2 cameras are 5D3s - so much of my comments are written with the 5D3 as my basis of comparison.
For the last few weeks I have used the camera at 10+ hockey games, an indoor training session, and outside in my backyard to get use to it - all in likely 1500 pictures.
I likely would never have bought the camera if I didn't want a sports camera AND I didn't already own two 5D3s which I use for weddings. I was seriously thinking about switching over to two 1DXs as I do not want to have to think while using a camera - I want everything in the same place so I don't have to think - thus I weighed my options, tried out the 1DX extensively at a store - and ultimately for me I went with the 7D2 to add to 2 5D3s instead of owning two 1DXs.
The two principle deciding factors for me were - more weight and too loud for weddings (1DX) and the added reach for Sports which is my current non professional gig (the 70-200 or 70-200 + 1.4x is perfect for me on the 7D2).
1) I have settled on shooting RAW and RAW because it is faster than RAW + Jpeg
2) Love the dampened shutter even at 10FPS - awesome
3) For non professional work, ISO 4000-6400 clean up well with noise reduction (this is impressive)
4) 2500 ISO, in my opinion, seems to be the high ISO sweet spot (very little quality give up for the low light capability)
5) 2500 ISO on a 7D2 = 3200 ISO on a 5D3 (but I think noise reduction works better on a 7D2)
6) With a combo CF Lexar 1066x and SD Extreme PRO 95 MB/s I can get 25-28 RAW files before filling the buffer
7) For AI Servo for hockey I have settled, for now, on Case 2 with Tracking = 0, Accel =1, AF Switching =0) - seems to work - basically this is lower Tracking (0 vs 1) and Increased Accel (1 vs 0)
8) There is 'something' richer about the images off a 5D3 vs the 7D2 - but what you can do in PP, especially wrt noise reduction, is very good with the 7D2
9) I love the fact that I did not have to learn a new camera - 5D3 users will immediately feel at home.
10) In extreme low light the 5D3 will grab focus with less contrast than the 7D2 - this is a very small effect and I had to experiment to show where it happens but a bigger sensor is a bigger sensor
11) I like the fact that you can EC even with Auto ISO but I wish you could do it with a dial without having to press the Q button (maybe I'm missing something)
12) I wish Canon would enable Spot metering to follow Spot Focus on the 5Ds and 7Ds - please? - I shoot almost 100% in manual but I would LOVE this function and it would really make me use AV mode - especially with Auto ISO and the ability to still EC.
13) I micro adjusted all my lenses to the camera and I am happy with focus
14) I think after 1000+ images of hockey I get about 70% hit rates with fast action using AI Servo and Back Button AF - it isn't 100% but it is good
15) The Sigma 17-35 1.8 makes for a great everyday lens, and with this lens if I didn't own a 5D3, I think I would be very happy with it and a 70-200 IS as a 2 lens setup (it wouldn't be a light setup however)
16) Haven't used the flash yet but camera works perfectly with the 600EX-rt - both on and off camera.
This isn't a camera for everyone but for me, a 5D3 user, if makes for a great compliment camera for sports. I may even pick up another 70-200IS and just weld it to the camera.
Overall, I would give the camera a 9/10 - it would get a 10/10 if the battery lasted 50% longer, the hit rate was 90% vs 70% while focus tracking and if somehow magically ISO 6400 was as clean as 3200.