I sourced an as new Kodak Pro Back on eBay - less than 40 acctuations and flawless. I was hoping to use it with my truck-sized Mamiya, but found that the required adaptor would cost as much as a new Hassy 555. Figuring that the Hassy would always be more desirable than a flat piece of metal with a hole in it, I sold the Mamiya and a slew of RB lenses and bought the 555. Still feels strange owning and using one - like being handed a piano when you're used to working with a cement-mixer.
Anyway, I have always enjoyed composing in a square, so I'm cosying-up to it. The 16mp back is producing superb output - noisier than I'd like it to be in the blue channel, but that's easily addressed in post-production. I bought a huge 40mm to be able to do wider shots, but it's the older version that performs well at infinity, and not so well closer-in. I have replaced it with a new 60mm, and that has pretty much become my do-all lens, along with the 80.
The lovely thing about the Hassy is that the option to do true wide-angle is there - just slap on an A12 magazine and the appropriate lens. Of course, the A12s also offer a cost-effective failsafe for the digital back (does anyone really own 2 digital backs of the same model, with one as a backup?) Presently, if I need to go wide, and maintain a digital workflow, I use the Pro Back with a Horseman Digiflex and some Nikon glass - kludgy, but it works.
I hadn't ever intended to own a Hasselblad - they've always seemed too-pretty and precise, to me. Yet the combination of a Pro Back and the 555 has proved to be a good route into medium format digital. Sure, Jo Schmo will be on my heels as the prices fall further on eBay - and the big league have been wielding their H1s and P25s for almost two-years. Yet, thanks be, our ideas keep us in the race, not merely printed-circuitry...