Michael's, issues with focus and loading may have more to do with familiarity. I started out in MF on box style slr's and I now find the backs and inserts a bigger pain than the Mamiya (6 in my instance). Focusing is similar to some 35 systems (as Aggie states -- very similar to a Nikon FE2) and easier to focus in low light or when compared to an slr lens of the same speed (the fastest lens you'll be able to buy is an f/4).
Changing lenses is a trip, but youíll never fog any film. You will forget to retract the curtain though.
The ability to use this camera handheld at very slow speeds, eas and speed of focus and portability make this a wonderful travel camera.
I know 2 photographers who use it (or the mamiya 6) for portrait work. Although the inability to shoot wider than f4,5 and the 150mm being a little on the short side are an issue. I have seen it used by many wedding photographers and I know one guy who uses it to shoot fashion. He had to plunk down 1k for an NPC Polaroid back to please the art directors.
The gist is that it can be used for more than a travel camera.
The meter on the 6 is problematic. It is narrow for the 50mm and wide on the 150mm. I find my self using the exposure lock (AEL) almost exclusively. I donít know if that is an issue with the Mamiya 7. I think I read that it is not.
The other issues with the Mamiya 6, that carry over to the 7, is the lack of close focus, difficulty in controlling DOF and using filters, specifically ND Grads and Polarizerís.
The items that you will appreciate the most over time are its eas of use and lens sharpness -- at least that is what i love about the 6 and suspect is the same for the 7.