i have enjoyed using my mamiya 6, which i have had for over ten years. it has been dependable, robust, and capable of producing images that make me look like i am a better photographer than i am...
i don't have any experience with the mamiya 7, so i can't share any insights with you on that. i prefer composing and printing to the square format or i would have looked more closely at the mamiya 7...shhh, dont want my pentax 6x7 to hear that.
along the way i have also used/owned/sold/kept various tlr's, pentax 6x7, hasselblad swc/m, holga, diana, crown graphic (4x5), and rolleiflex slx & 6002.
periodically i go back and forth between the mamiya 6 and my leica m6 & 35mm f2, or leica cl & 40mm f2 or oly om2 or nikon f2, and some other 35mm cameras and have come up with some pretty good images.
first off, i am not a very technically oriented or skilled photographer. over the past year or two or three (?) i have come to prefer the "medium format look" - for me that is the increase in tonal range, what i see as more sharpness, and images that generally look as good at 10 x10, 15 x15 or 20x 20 as they as 5 x5's. i have printed 35mm, various 120 formats and 4 x 5 when i worked professionally and for myself.
sorry to go on and on, i just want to give you some background on how i have arrived at using the mamiya 6 as my daily camera. there is the so-called delicate winding mechanism - that has never been a problem - although i believe some folks have experienced that problem. did they have a flawed camera or one abused by a previous owner ? who knows. then there is the issue of the non-through-the-lens metering system. again no major problems there, i have always regarded the meter readings to be suggestions and use my fuzzy non-technical brain to sort it out. some complain - myself included - the lens selection is too small, the lens speeds too slow for low light work, and the close focus distances preclude "close focussing".
it would have been terrific to have a 40mm or 60mm to chose from...oh well. the upside to having only the 50mm, 75mm and 150mm focal lengths is it keeps the gear volume down and makes one think a little more about how to pre-visualize and translate that to the "right" focal length. the upside to the slower lens apertures is it keeps the lens size and weight down. the close focus issue...hmm, no upside there. to bring up a small detail, that is one of the times i'll use the advantage of the larger negative size. i'll enlarge that area as much as i can - up to a point.
wow, i am on a tear here...brevity has never been my strong suit...
since you are already a rangefinder user you know well the strengths and weaknesses of the breed. it sounds as though you will not find the fewer exposures per roll to be a hinderance. i suspect there may be a mamiya 7 or 6 owner out there that would looove the trade you mentioned.
feel free to give me a shout with any questions about the transition you are out to make.
breathe, relax, and enjoy...
happy trails,
kenneth