i use a bronica, just got a metered prism for it and its a total weapon! i love it its like an SLR on steroids. I decided MF over 35mm because the depth of field can be much narrower for the same aperture and with my bronica its square format which i love.
Im raising funds for a bike frame so selling my 35mm f2 and 85 f1.8 lenses rather than selling this, thats how much i enjoy using it. As for efficiency then unless you're getting paid to take photos its all more or less for personal enjoyment, if you enjoy mucking about with film then result.
if you're near derby youre welcome to have a shot of the bronica
EDIT: if you have a D700 and D300 plus good glass the film and processing costs arent going to break the bank plus get yourself a tank and darkroom bag (im selling one btw) and its even cheaper.
2ND EDIT: there are a few pics on my flickr (click my name) from the bronica, i tweaked them cos i fluffed exposure but im getting better.