As a proud and very happy 645D user, I have to underline the importance of the above points about support. I live in Australia and was unfortunate enough to have had a problem with the body a little while ago that required repairs. Pentax (Ricoh) themselves have no relevant facility in Australia - just a relationship with a company called C R Kennedy who can do some things themselves - so anything complex or subtle or requiring spare parts means the camera has to be shipped to Japan and back. My camera disappeared into a black hole for over 3 months without a loaner or even any concrete idea of when I would get it back. Language barriers between C R Kennedy and Japan did not help either. Calls from me (to C R Kennedy) were either not returned at all or, when I eventually got impatient enough to escalate things, were simply met by assurances that it would come back as soon as possible. This is clearly not good enough for a pro spec camera. They need decent local support, the ability to resolve things themselves in country (for anything other than major major things), loaners and people here who truly understand what is going on. In short, professional standards of support.
The 645D is a brilliant piece of kit and very reliable. I have every confidence that the 645Dii will be excellent as well. But they really need proper, global (i.e. local) support if they are going to succeed in this segment.