To be honest, the only reason I left the AFDII was that the DB never arrived.
I know that feeling. I had a P45 coming from Capture integration, and the courier company have lost it (they say they are trying to find it again!) This is bad, since there seem to be plenty of Hasselblad fit P backs around, but few Mamiya.
I feel your pain about the discontinuation issues, but lets face it: either of the two systems will do the job well. I felt the choice was 50/50, and went for the Mamiya, since the lenses seemed to be 'nearly as good' as hasselblad, but a lot less expensive second hand. Also seemed to be a wide range of lenses available. Need a back, 'cos I have about 12 lenses (including a fair bit of duplication) and I want to narrow that down and sell the rest, when I've thoroughly tested them.
I'm looking forward to your comparison of the two systems. the 645 has that Achilles heel of no decent finder. I hope I can live with that!