I am no expert but I have not heard of any problems with shutters or with the 80mm lens. My lens is from an old 500C and is excellent as are the mechanics (I have the 501CXi). The shutter speeds appear to be correct as the exposures are right on. THe sharpness and contrast cannot be beat.
Two of my older backs, not A12's but just 12's, developed light leaks due to deterioration of the felt light traps. These were easily repaired by a nearby repair shop.
I love the camera and use it for both B&W and color. It is very solid, everything fits and functions well. They will have to pry it from my "cold, dead hands".