In regards to the grip and viewfinder, if I were holding a ZD or 645D 9 hours a day, I'm sure my opinions would be radically different. To me the ZD and 645D are a "bridge" product - like a psuedo medium format cameras in a dSLR format. It's smaller, easier to pack while on vacation, etc. In this regard I think Mamiya did an excellent job with the ZD. And if Pentax and Mamiya are targetting the enthusiasts, semi-pro's, etc., then price is key. When Pentax pulled the 18 MP version, and they the Hoya announcement... I thought the 645D was dead. So, I'm quite happy to see it's still happening. The more choices, the better.