i own a P30 and use it with 645afdII and RZDII....the 645 does everything the hass sytem does except for the synch speed....the RZ gives me a few options the hass can't give me and the synch speed (ok "only" up to 1/400)...actually i shoot in LA and did a shoot at noon in full sun the other day....had no problem making the sky dark (1/125@ f16)...and for anyone looking for shallow depth of field PLUS outdoor sync, i guess the Hy6 (iso 25 with 1/1000) is the only option anyway.....
the 645afdII is a great, proven, simple camera, which can be adjusted in more ways then i would ever want.....the H can be adjusted just as much, but you might need a manual to turn it on (the first time i EVER had to look at a manual to go from P to M) but i am sure that is manageable....i just like cameras to have the buttons and dial where they all have them.....
yes the 645 is "plasticy" but so is the H, the buttons on the H are the cheapest i have seen on any camera, ever....
the lens range on the mamiya is nice, the prices are a dream....the H is a bit limited, and steep.....(the new mamiya lenses seem to follow that trend)....
the H grip is too small for my hands, and the lenses are very heavy....both systems need what contax and every DSLR have....a vertical grip.....
i have shot with the H a couple of times, i don't see a difference between the mamiya 645 and hte H lenses.....i do see a difference between the RZ lenses and the both 645....the RZ are a step up IMO.....
AF is more or less a joke on both, the finders are better then canon/nikon, but nothing compared to looking into the RZ.....
every time i shot with the H, there were problems....nothing that killed the shoot, but annoying.....i have yet to have ANY problem with either one of my 645afdIIs or the RZ or the lenses......
the only reason i could see to buy into the H system is to go hass all the way and get a H3D....take advantage of the software correction and hope that future developments will prove it to be the winner.....
for anyone going phase, leaf, sinar,...i don't see the point of buying into a system that is (more or less) dead for your back....there won't be any new lenses for any of these backs and those lenses would be the ONLY reason to buy into the H system in the first place......
there is a rumor that C1v4 will have lens correction built in for the mamiya 28mm....whenever that comes out....who knows....it is pretty obvious that everybody else will come up with something as well in the long run....