Yes, the Superwide is a dream camera. It's also ungodly expensive even now. For the price of a Mamiya 7 and two or three lenses, you'll end up with a Superwide.
Got mine for $750 and I love it! It's one of the older models, but I don't think that matters much. Highly recommended. I've compared it to the Hasselblad 40mm and the SWC wins every time.
I would also recommend looking at a Hasselblad system - they are amazing, and much lighter than a 6x7 SLR. The RZ system is good, but gets heavy if you try to carry a couple of lenses, backs, a prism finder, etc.