One millimeter or so shy of true “full frame” 645 format, the newly-announced late-2008-availabilty PhaseOne P65+ offers sixty (60) megapixels (8984 X 6732) along with 12.5 stops of dynamic range in a huge 53.9 x 40.4mm sensor, about 20% larger than previous medium format sensors (see pdf comparison).
All of this comes at the very reasonable price of roughly US$42,000 for back, body and lens (reasonable in comparison to existing medium format digital offerings). The PhaseOne back ought to make Hasselblad squirm, with 10 more megapixels, a 20% larger sensor, variable resolution, and a non-proprietary system.
While the H3D-II-50 is priced US$2000 lower, that is of little consequence in light of the overall system cost (additional lenses, etc). Image quality might be the defining factor in the end for some, and for that we’ll have to wait and see, but I’ll place my bet on PhaseOne, a company with customer-appreciative policies for upgrades and inter-operability with multiple camera platforms.