While a bit late to this thread, I just wanted to add that many people find the vibrations in the Pentax system to be problematic, even with the mirror locked up on a sturdy tripod. I initially had three of the 67/MLU bodies (precursor to the 67II), two for film and one dedicated to a Polaroid back. Upon returning from each distant location shoot, I'd nearly pull my hair out at the number of frames that had issues with vibration (often the right side of the frame). I eventually gave up on the Pentax 67's and went to Horseman SW cameras with rollfilm backs - worked great but not a very fluid solution for most people.
Pentax then came out with the 67II, which promised better vibration dampening, 1/2 stop shutter speeds, and a few other features that were more marketing than practical. I figured I'd give it another go as most of my work at the time was best suited to the compactness of that system vs. some of the larger 6x7 competitors. Well, the 67II was indeed nicer than the 67, but there were a number of shutter speeds (1/2-1/30th) that were all but impossible to attain a TRULY SHARP image at. No amount of mirror lock-up or 75# tripod is going to dampen that huge shutter (forget the mirror, the shutter itself causes issues). After returning from several major shoots overseas with models in tow, and reviewing the images on the lightbox back home, the second experiment with Pentax MF came to a close. The lenses I owned were the 35/45/55/90/105/200. I never used the leaf-shutter lenses intended for the Pentax 67, those may be the ticket for subduing the vibration. That said, I can't be limited to just those lenses.
The optics themselves are quite good, the 105 is rather amazing.
