@ tkmedia
Some years ago, I had a Mamiya 645 1000s. It was a complete enigma to me. I'd owned Mamiya kit previously and I knew how good the lenses are. However, what I hadn't twigged by the point I bought it was that:
(a) there is no "back" to change - so you can't buy a spare and do slide and film shots in the same session without going through a whole film and reloading
(b) as it's a 645, using it in portrait mode is all-but impossible unless you have the prism finder. Even if you do have it, you've still got to turn it on its side (a faff) and make sure you've set the buttons up properly because once it's on its side, you can't get to them easily without retuning it to the landscape orientation.
The photos were fine and the camera worked faultlessly. I just got narked with it and eventually traded it for something - though I can't remember what.
It didn't make my arms hurt, though. Just got me mad. Give me a square format MF any day....
Nevertheless, persevere if you can as the build is great and the lenses are superbly sharp and contrasty.
Paul.