It depends what you're shooting, too. Landscapes? Totally. Toddlers running at high speed between bright sun and full shade? Not so easy. (Yes, I know it can be done, and someone will doubtless post such thing to prove it!)
As to Klunkiness, if you're used to setting shutter speed on a camera's top deck, and frequently consulting DOF scales etched onto the lens barrel, then the C330 with rim-set shutter speeds on the side of the lens barrel, and the weird DOF bar on the side of the camera, does require some learning. TLRs like your Favorit or most Rolleiflexen or the Yashica 124, with at least a heads-up display of shutter speed and aperture, can be a better ergonomic first step away from SLRs or conventional rangefinders like your M3/M6.
Remember the trade-off with the Mamiya is that in exchange for bulk you get lens interchangeability. I'd recommend getting one or two other lenses (besides the 80 mm) and see if you use them. If you find you're always using the 80 mm anyway, sell the Mamiya, stick with your fixed-lens 75/80 mm TLRs like the Favorit and save a kilo of weight in your kit. I find I almost never use my 135 mm (my only other lens), although long was probably the wrong direction for me; I'll likely get a 55 mm or 65 mm and see if I use it, as a last try. If not, the Mamiya's going on the auction block now I've got a Rolleiflex.
Finally: You can stabilize the C330's bulk with a grip that screws into the tripod bushing. Mamiya's grip might be more pricey; a cheap generic one probably won't have a shutter release linkage.
--Dave
