I have found the Pentacon 6TL to be a reliable workhorse. I have 3 of them that I have been using since the 1970's. You can break any camera if you operate it incorrectly. I use Kiev metering pentaprisms on my Pentacons.
The feature I most dislike on the Pentacons is their tripod mount. It is difficult/impossible to keep the camera from rotating on the mount.
I also have a Hassleblad 501 CM system that I have been using since 1981. Nice camera, but the lenses (and backs) are very expensive. The Hassleblad lenses are not that much better, in general (if at all), than their much less expensive Carl Zeiss Jena counterparts that fit the Pentacons and Kievs.
I use a Kiev spot metering prism on my Hassleblad. However, I rarely ever use my Hassleblad or the Pentacons any more since I have two Kiev 88CMs. One camera is an ARAX from Gevorg Vartanyan (i.e. ARAX) in Kiev. The other is a Hartblei from Mike Fourman (Kiev Camera) in Atlanta, Ga. Both cameras (and companies) are reliable. I have found the mail service from the Ukraine to the USA to be reasonably priced and reliable.
I believe that the ARSAT (Ukrainian) MC 55mm f4.5 Perspective Control lens is the best WA MF lens currently available in the P6 (Pentacon/Kiev) mount. It is better than my 60mm Schneider MC Curtagon, better than my 50mm MC Zeiss Flektagon and better than my 50 mm Zeiss Distagon (Hassleblad). The ARSAT 55mm lens currently sells for $349. (from ARAX).
Check out the Kiev Report: http://forums.delphiforums.com/kievreport