All the Zeiss F-fit primes I've tried have been stunning: they make my D70 look an AWFUL lot better than the kit zoom, and somewhat better than it looks with my 90/2.5 Vivitar Series 1.
I hope the 58/1.4 (which I haven't tried) is modelled on the 58/1.4 Nikkor (which I had and loved) and not the 58/2 Biotar (which I have, and which is somewhat stronger on character than sharpness, though the latter is still pretty good).
I sold my f/1.2 F-fit Nikkor because I saw no real advantage in an extra half stop on a reflex. Like many people, I find I can hold an RF camera still for about one shutter speed step longer than a reflex, so f/1.4 equates to f/1.0 and f/1.0 to f/0.7. In low light, rangefinders simply wipe the floor with reflexes as far as I am concerned.
Cheers,
Roger