I have the FA43 as well as to FA50 f1.7 too, needless to say the FA50 has not touched the camera since I got the FA43.
Its the second FA43 I have owned, and this brand new one seems super sharp wide open, where as the older second hand one never seemed that sharp @f1.9 in the centre.
I have been using the FA43 on my MZ-S and its a dream combo, light, compact and just the perfect single lens for walking around with. Wide enough for general shots, fast enough and long enough not to distort faces/people for impromptu portraits and just a lovely combo!
Examples on Film and K-01 (both wide open)
And just because: