Dave, Although the Pentax 120mm 645 macro is superb, trying out some of the other Pentax medium format lenses isn't redundant in my opinion. When I tried various 645 focal length lenses on the D800e, I was surprised at their level of performance even over many of the excellent similar focal Nikon 35mm format lenses. I attributed some of the look and notable imagery to the fact that the D800e was using the sweet spot of many of these 645 format lenses. Of course it's on a lens by lens (case by case) basis.
What's so convenient about most all of the Pentax legacy 645 lenses as you noted, is that they all have aperture rings, so you have a choice of selecting shooting aperture.
Dave (D&A)
Thanks for the tip Dave. Right now I do not have a Pentax 645 -->Sony NEX adapter. I do have a Pentax 645---->Nikon adapter + Nikon ----->Sony adapter which I could try in series. I know you have accumulating tolerances, but I would think live view focusing would eliminate any focus issues. I will give it a try.
Regards
Dave in NJ