The matter is that that this cropping turns normal lenses into long focus lenses and it means that we cannot get wide angle and enough perspective and lack of perspective means that shots become flat. They lack volume. That's why probably photographers using digital backs shoot only in studios and mainly people models coz long-focus lenses are needed for portraits and it is ok. But as far as artistic photography other than portraits, fashion and glamour is concerned, wide angle is required! Why? Coz you can crop images later in photoediting software. But you image will not look flat, coz when you were using wide angle you could shot far objects and close objects simultaneously, while you cannot do it quite well with long-focus lenses. That's why i am thinking hard what is better to buy canon mark II or digital back H20.
If i have canon, i can use even fisheye, any angle i want and 35 mm full frame is still good to have good tonal ranges. I don't actually know if such backs as H5, H10, H20 have richer tonal range than canon, i doubt that. Some people claim that no DSLR including mark II is capable to create such tonally rich image like even the cheapest H5 digital back but they only claim and do not present any evidence of that. Of course, P65 back will be superior than mark II coz it's almost full frame MF but who can afford this?
Some people think that MF zeiss lenses have best Boke. But boke is the last thing which makes a good photograph. the main thing is composition and to make a good composition you will need a wide angle lens.
Some people think if they get the lens with good boke all their shots will automatically become masterpieces. By my own experience i may say it is far from the truth. I think most art photographers will agree with me about this frustration.