I've been using my Zf for a couple of days now, mostly with MF lenses : Summicron-R 50/2 and Voigtlaender 180/4, two of my favourites.
I am pleased.
Focussing aids are excellent. The Voigt was not that easy to focus on the Df (dark image) but on the Zf (and Z6ii too by the way), no problem: EVFs are fine for ageing eyeballs. Magnifier was assigned to the front Fn button, the position of which I slowly get accustomed to. Above all, the face detection system and the possibility to zoom instantly to the detected eye works great, even on statues or pictures of humans : very fast detection, and apparently very few "false positives".
IQ seems better than the (to me, good but not overwhelming) Z6ii, and subjectively closer to the Df. Noise behaviour seems better than both. The high-ISO in-camera JPEGs are considerably better (no salt & pepper, quite apparent on the Z6 ; no mush either). The processor, rather than the sensor, seems to be the cause.
Other than Ilkka, I never had bad experiences with SD cards, be it for photo apps or (in the shape of micro SD) as secondary drives - the M$ Surface laptop has a slot for such cards, and I used 64GB or 128GB storage not just for backups, but mainly to host big files (e.g. movies and copies of photos). I'd by Sandisk out of superstition maybe, because they never failed me in the past, so I bet they won't in the future. I definitely had trouble twice with CF cards though, last with the D700. Anecdotal evidence does not replace statistics, but never fails to impress.
You may by now have guessed the colour of my Zf...