I don't own the 43 but I do have the 31 and the 77. I would not part with either one.
I use them most of the time with my PZ1p, but I also like the 31 with my digital because it is close to the same perspective as a 50 on film.
They certainly aren't perfect, but they are extremely well built, and the image quality of both the 31 and the 77 are very hard to fault. I think that this little article by Mike Johnston at Luminous Landscape puts things in perspective quite well.