A friend's band was coming through town the same day my Z6 arrived, so, after a bit of menu twiddling, I took it out for it's first shooting. All with Nikkor 105/1.8 Ai-s, at f/2.8 I believe.
Some of my first impressions were expected. IBIS, Peaking and Zoom are incredible additions to a manual shooter. I found Peaking extremely helpful, as focusing fast moving subjects in a dark under show lights is often difficult. Especially since glaring red lights are common which make it difficult to focus in an OVF as it makes white people look like mush. When I first fiddled with Peaking at home it seemed to "engage" very little, until I switched to Flat picture profile with Sharpening cranked (I shoot raw) which got it going.
As far as being an effective imaging tool, it is certainly an upgrade from the D750, but in terms of control it is certainly a few steps back. There were times where I had to toggle between using the D-pad and the rear Command Dial to do things that feel like it should have all been on the D-pad, for example. And some of the custom button options are disappointing, like the OK button only being able to Zoom/Reset AF Point. I want neither of those on OK, so I have a button assigned to useless. I hadn't noticed the Z6 is missing a Metering button before getting mine, which is a small disappointment. The Drive/Menu buttons are very awkward as well. Boy am I spoiled by the D750's Drive wheel. Overall, worth the upgrades. I'm guessing some of the control crippling is Nikon's way of ensuring I'll want the Z6 2.0.
Lastly, the inability to see my selected aperture . . . for most shooting situations it's not a big deal. But in a dark show, downright terrible. It is a serious shame that Nikon did not design the FTZ to deal with this. Not a deal breaker, as I shoot shows in manual without changing aperture usually, but it would make responding to an opportunity that requires otherwise very slow as I need to pull out a light to look at my camera. Looks like getting my lenses chipped is simply not optional any longer.