A fine lens, it seems, at least on Df (16 Mpix). AF is reasonably fast and MF reasonably smooth, remindful of the Sigma "A" lenses. AF and stabilizer are triggered by the AF-ON button on the camera in my case ; it is possible to (de)activate the stabilizer and/or autofocus via the two lens switches. Sharpness, vignetting, coma all are satisfactory. Distortion is low, but (similar with 50/1.8G) seems to "bend the corners", i.e. to increase there. So for architectural shots, you may forget about distortion correction unless there is really something going on in the corners. There is some CA (easily removed) and some LoCA (less easily), but not that much.
The stabilizer works at least down to 1/4 s, but in this case one had better duplicate shots.
In the test shots below :
1) is a strong crop of a pic exposed 1/4 s, wide open. Focus is on the trash bin. Purpose was to test the combination sharpness + motion blur. Passed.
2) is another shot at 1/4s, 100 ISO, f/2.5, completely unretouched.
3) f/1.8 again, focus on the polyester "skin" in the foreground, to show the OOF highlights. Some onion ringing can be seen iin the darker highlights.
4) interior of a tunnel at f/8, 7200 ISO, 1/8s exposure, all handheld and stabilized of course.
So for night shots that's a winner. I'll try and get some "moody" ones as soon as we get fog, to see if Kertesz or Brassai would have adopted it