I'm using the Mitakon on an A7II since last saturday. Overall I'm really happy with the general look of this combo, very Leica like in some shots. I did not figure out yet why this 'look' is significantly more present in some pictures, it does not seem to be 'aperture related' only.
What's less funny is the loss of sharpness out of the center frame at large apertures. At first sight it looks like the main subject must be centered if larger than f2,8 is used.
Anyway, really funny to use so far