Holy cow! You guys are awesome!!! So much information. Well, I tried to process as much as I could and narrowed my thoughts down to this:
Pentax 67 - Better outdoors? Not modular.
RB67 - Fully modular, cheaper, and just as sharp?
RZ67 - Same as RB but with electronic shutter (better accuracy?), 'one-motion' frame to frame and I read its use is more intuitive than the Pentax?
Ultimately, I couldn't get past the Pentax not being modular. Also, after reading more about the RB/RZ I understood how awesome they are! Unlike my 600 shots/10% accuracy days with digital, film has taught me to be more precise with my shooting and it's really helped my success rate. That said, I do believe I would want the option of switching from, say, color to b/w mid shoot. Or even different films to narrow down a favorite? Oh, and not losing any chemistry with my subject having to reload film if I have a few backs. Also, the camera will live on a tripod 95% of the time so the weight/size is no prob.
I was looking to spend around $600 - $800 and there are TONS of options in that range. I decided I liked the few extras of the RZ over the RB and you'll all be excited to hear that I'm currently the high bidder on an RZ Pro II with a 110/2.8! Wish me luck gents!
Wish I could buy you all a beer! ;D