...and what you use them for?
Damn near everything, 'cause I'd take a bath trying to sell my beloved Contax 645 system with my eager but kludgy Kodak ProBack hanging off its rear. I love the ergonomics and ruggedness of the camera, love the lenses, and have been able to work around the back's considerable functional/ergonomic limitations.
System excels at portraits, studio-type stuff, and general shooting. Limited architecture. Biggest street shooting system this side of an 8x10 view camera, and almost as easy to tote!
Heck, I use it for stuff for which it is wildly inappropriate, in lieu of flagellating myself with a scourge as I march around in a circle chanting dirges. For example: I shot an equestrian event this weekend with that big a-- 350 on a monopod, looked like a field artillery piece. (Yes, 5-9 fps would have been handy during the stadium jump and cross country events, but i did catch a few in mid-jump using my Mark One eyeball and index finger at about .7 fps.) We're under the approach path for UPS's home airport, so I half expected Homeland Security to show up to confiscate the beast.
Also shot a bunch of skaters at an extreme sports park, same rig as the equestrian. A few kids asked me if they were going to be on TV! Think I blew out a disk in my back trying to climb out of a bowl.
Just can't bear to part with the thing for the D200/D2x that would be so much more suitable for a lot of my shooting.