I took some 1600 pics yesterday of the night of the arts in Helsinki with the Zf, and didn't run into any focusing issues that I could identify as firmware-related. I did have the usual problem that sometimes if the subject is far out of focus in the foreground, the camera will not pick it up very quickly, and has to be sort of "forced" to notice that subject instead of potential background subjects, but that was not happening more than usual. I used 35 mm f/1.8 and 135 mm f/1.8 lenses, mostly wide open; the fast apertures may contribute to the positive outcomes in some cases.
The camera is very nice to use with the smaller lenses such as the 35 mm, but with the 135 mm it was a bit too small for optimal comfort. Generally I think with the 24-70/2.8 it is OK, as well as with all of the f/1.8 primes up to the 85 mm. With the 70-200/2.8, 135/1.8 and longer it would serve as a backup camera but not my first choice. I do enjoy greatly using the Zf but for larger lenses I think I'll just use the Z8 and vertical grip. On the other hand having two bodies and larger lenses does increase the overall bag weight and eventually it becomes less fun to carry and use than having just lenses up to the 85 mm f/1.8 in the bag, and a small camera.
