I preordered a Nikon D500 and it just came in. My first impressions are ergonomically its really nice to hold and feels solid and well built. I got the vertical grip with it which makes it feel even better. The buttons are a bit different for me (Im coming from a D3) but thats not that big of a deal.
Personally I think the RAW images come out kind of flat but there is a ton of data in the files that easily allows you to really make them pop if you edit them in in LR or ACR.
The auto white balance is different for me. There are 3 different auto settings one for cooler, one for neutral, and one for warmer which threw me off at first because it was set to the cooler auto setting.
ISO range is ridiculous. There is visible noise but honestly the noise at 51K looks about what 6400 on my D3 looks like.
Haven't played with the video much but I did do a short 4K clip last night just to check the straight out of camera quality and its really awesome.
The autofocus system is incredible. I shot a half marathon this morning and out of the 800 shots or so I think I missed about 5 (using continuous AF).
So far Im very happy with the camera and once I figure out what all the features do Im sure it will be even better. Ill be doing a full review in the next week or two.