A few early impressions. Still haven't had time to shoot more, but a bit was possible.
1) The viewfinder
Looks like to be one of the highlights of the camera. If compared with the D7200 and D800, the impression is that it is about the same size as the D800 viewfinder. In addition, that the clarity and contrast of the D500 VF seems to be better than the one in the D800. I like it, as the viewfinder is one of the critical components of a camera for me - as I need it most of the time.
2) The handlebar
I like the deep recessed form of the handle - similar to the D750 (and better than the one on the D800). The probability that the camera slips out from my fingers when carrying only with finger tips seems to be very low.
3) AF coverage is really large
4) Weight
I mentioned it before, but this impression comes back and back. The camera is light. Add to it the smaller DX Telelens options and the advantage grows vs. FX bodies
5) Speed
In most aspects, the D500 is as fast as the D4, sometimes faster (AF, XQD, ..). I am using the second 2933x 128GB XQD card in this camera and the D500 behaves like the D5. Whatever I shot, the writing was done when I released the shutter. Which means: I don't need to spend ANY attention to the buffer capacity. This wasn't the case with the D800, D750 and D7200 (for my style of shooting). Not that I always need this buffe capacity, but when needed - it simplifies things.
6) ISO Sensitivity
I might get old, but I don't see it particularily insightful when there are long discussions about high ISO performance of contempoarary sensors. Most sensors are so close to each other that the subtleties don't matter in most cases any more. Ranges up to ISO 3200 on DX are well usable in most circumstances and if needed all cameras can be used like in the "good old" days when there wasn't an ISO dial on the camera body.
7) Flicker reduction
Hey, I like it. If I am not wrong, the first Nikon DSLR with this feature. Not the most important one, but one more feature to avoid pressing the butter at the wrong time when lights were flickering with 50 or 60 Hz.
8.) EFCS
Like the D5, the D500 has the slightly improved EFCS (Electronic front curtain shutter) of the D810. One more thing to reduce shake and vibrations on the tripod (just use it with 3s shutter delay).
9) Size
The combo D500 & AFS 300mm/4 PF is a size/performance winner. The camera and lens look so small, yet the performance is good - very good actually. Just give it a try.
rgds,
Andy