I use medium format digital for jewelry work, not film, I have moved to a point that almost no film at all. I am using either P45+ on Contax 645 and adapter to Sinar P3, or Hasselblad H3D39, and sometimes use 1Ds MK3 for less demanding clients. The benefit with today's 39 million pixels back is extreme quality, but the problem is only little DOF can be achieved, unless you are working with digital back attached to a technical camera platform that provides movement. For P45+ and H3D39, the best aperture to use may be just around f/11, or wider, sometimes you may go as far as f/16 on some lenses, but beyond that you will probably shofting the image, and with a close up image, f/11 means the DOF is measured in mm,not cm. The best solution, if not wanting to go on extra miles to invest a technical camera system (and those beautiful German leaf-shutter optics), my solution is to use multiple shots of varies focus points and then assemble them together using softwares. You may check on this:
http://www.heliconsoft.com/In my point of view, the digital back gets cleaner image and of course sharper images and more accurate color than film can do - sorry, not want to raise arguments here, this is purely IMHO. Film has other merits that digital capture can't reach, and vice versa.