I have had a Mamiya 7 outfit for 10 years with all of the lenses. As everyone has stated, it is simply a superb system for a careful worker who values wonderful results.
Sandy, I can even make a case for the 50mm with the outfit you have. There are times when 50 is perfect even with the 43 and 65 in the bag - the subject, distance, impression just look better with the 50. They are small enough that you can carry them easily. My two bodies have been all over Southeast Asia and China; another advantage of the system is that it does not look "expensive" compared to motor-driven, long-lenses super SLR's. I had a driver in Yunnan province ask me what I was doing with such an "old" camera. You can see his cousin in the rock quarry picture in my Asia gallery at
www.georgepappas.net.
I have Verichrome Pan/PMK (now I will test pyrocat) negs that are simply amazing in their tonal quality from this system. It is a unique system.