FWIW, .02$ in addition.
I agree with what Eric says, not surprisingly as we have matured through our Rollei/Hy6/dp20/Leaf transition as a mutual support group. A few things from a less sophisticated user, who has no experience with the Hassy or Imacon backs:
- the Leaf back on the Hy6 is quite a bit more easy to use than the dp20 on the 6008. The integration is practically flawless, screwups happen (by and large) only from empty batteries, and almost never from the camera end. It works well.
- the 6008 impressed me as much more robust than the Hy6; that said, the 6008 sits and the Hy6 is used. Once you get used to the Hy6, you will not look back, except fondly on the 6008 as a simpler and more mechanical era that somehow warms the soul more than the new world.
- the Hy6 has a depth of capabilities that just keeps expanding as your work grows. The list is practically endless.
- the Leaf backs are quite good - and it is possible to explore the subtleties of tones very delicately with them. There is a learning curve, and like Eric, initially I liked the tones of the dp20. Now... not so sure.
- I never got really comfortable with the dp20 on the 6008, there just seemed to be a few too many issues: mirror flop, lower ISO, a lack of electronic coordination, all of which went away with the Hy6.
But there is a simplicity to the dp20, and a loveliness to its unaltered files right out of the box which is fondly recalled. If you can deal with the file size, and the light needs of fat pixels, its a nice way to go. But don't underestimate the Hy6 and the capabilities of the Leaf backs - lets just say the M8 sits these days with no use whatsoever. The standards have been raised much higher.