As stated in my original post, I'm a dual format returnee too, though I can't claim to be a particularly accomplished one. I've never used anything but film for hobby work, as I see no advantage to digital below the level of a MF back, which I can't afford. And I've returned to film for point-and-shoot.
By the way, speaking of MF digital backs, my understanding from Luminous Landscape and other sources is that MF backs mostly solve the problem of digital look, from clipping, because the dynamic range is wide enough to expose for the highlights and still have detail in the shadows; the digital look from the linear character of the sensor is solved in processing, leaving clipping the main contributor to the look as I understand things (which may be imperfectly). There is the question of tone as well, I know, and ink-jet versus wet printing, but there too, the differences are not huge from what I've seen and read. Don't get me wrong, it still costs $30,000 in digital to replace a $1,500 film setup, but I'd bet if twenty-times the cost were not an issue, most (not all, of course) would turn to the MF back: a 6x4.5 sensor gives greater depth-of-field options than 4x5 film; autofocus on a high-end digital camera seems a nice option; and there is the option to work much faster, always an issue (at least for me) with light always changing.
Nobody makes a 6cm x 4.5cm sensor it would probably cost closer to $120,000, most digital backs use a sensor that is roughly 35mm sized. The issue is that like any other type of silicon chip, there is a limit to the number of defects allowed, so a large percentage of units made, end up failing at the quality control phase. The larger the unit, fewer units you get on a wafer and the larger the chance that a particular unit will have too many defects to be usable. Medium format backs however, don't really affect the choice of film cameras, because the camera is the same, the back is different. There are so many MF film backs in circulation, and they are built so well, that even if they stopped making them today, the supply would probably last into the next century.
There are other issues though with MF backs, first is that a 30MP image, means a data file of at least 120 million bytes in size, at 14 bits per pixel you usually round up to 16 bits for storage, which means 240,000,000 bytes or 228.8 MB of storage per image. The typical 700MB CD-R would hold 3 images. A DVD-R would hold about 21 images a dual layer maybe twice that. You can use compressed storage, but that means taking the time on the computer to process the images, and don't forget, the bigger the images, the more computer power you need to process them in a reasonable amount of time.
The digital look comes from three factors, dynamic range is only one of them, the lack of grain is another and lack of tonality is a third. A 14 bit image has 16.384 discrete tones it can reproduce in each colour for each pixel, a film image has an infinite number of discrete tones it can produce.
I find that most of the digital comparisons to film are done from the digital side, which gives it an advantage, they scan the negative or slide and then do everything digitally from there. None actually take a digital image and a film photograph at the same time, of the same scene, process them appropriately using the appropriate technology, then make a print and compare the prints. Yet a digital or film capture is not a photograph. The photograph is the finished print. I expect a digital scan of a film image is going to have many of the same issues as a digital capture, including the issues of dynamic range and lack of tonality.
Many of the modern features of modern digital cameras, such as auto focus, multiple kinds of auto exposure, also apply to modern film cameras. Many of the modern DSLRs with live view use two sensors, the small viewfinder sensor could probably be added to a film camera as well, giving you the ability to get the advantages of digital with film capture.
