I could test a Z7 for about 3/4h today. The lens was a Summicron-R 50/2 (adapted to F-mount), so I had to work in stopped-down mode.
EVF is comfortable to the eye. It gets a bit muddy when stopping down to f/8 in a dark place - well, that's hardly surprizing. When using focus peaking, manual focus is relatively easy, but the Df is at least as good in that department. Using magnification seems indispensible to get pinpoint focus accuracy. Using the ill-placed (+) and (-) buttons for that purpose is a pain in the neck, though. I wish there were a loupe function at half-pressed shutter release, but could not find it.
The stabilizer works reliably down to 1/8s. Consistently getting sharp shots at 1/4s proved more difficult; for that purpose, I activated the silent mode, electronic 1st curtain, and 0.2s shutter delay, and all was fine. Stabilization is very good, but not overwhelmingly so: I could get the same result with the Tamron 45/1.8 VC on the Df, and could go down to 1/2s with the Olympus E-MD OM-1. Still, it is a useful feature. Combining stabilizer and magnifier indeed allows precise manual focussing, and that's essential.
Needless to say, image quality is outstanding. Lots of pixels for sure, but darn good pixels. Cropping is certainly an option with that sensor.
Handling is OK. Probably a bit better than the Df (rudimentary grip!), but still not the best fit for my hand. Menus are similar to Df, I'd say: so-so. Customization is possible, and needed.
Bottom line : I think I'll resist the NAS. But that's because the Df is so well-designed. I'll probably wait for the next iteration, hopefully with better battery life and a half-pressed-shutter-release-loupe-mode. If you do not have a Df, beware...