A drum-scanned medium format image is an amazing thing. I agree that starting with that level of detail would blow away a digital camera, and those to come for the next five years. Of course, a drum-scanned 6x7 image can cost up to $50.00 USD. It makes a digital image so large that only a few will fit on a CD-ROM disk. Film still has advantages, especially when it comes to massive amounts of very fine detail.
But, I no longer feel that medium format (MF) is necessary, unless you are a decor photographer. I used mine primarily for weddings and some scenics. I compared images from Fuji NPS (120) and the D100, and for normal 8x10 and 11x14 blowups, the D100 looked better, hands down. NO GRAIN, very very smooth. I suspect that moving greatly beyond 11x14 would cause some image degradation. But, at that print size (maybe 20x24) decreasing the DPI from 300 to 240 or even 200 will keep the image very nice, viewed at the normal viewing distance that a large print needs.
Medium Format is going the way of Folding Cameras. It is too slow, too expensive, too heavy, etc. Have you checked eBay's ads recently? A good portion of the ads for medium format equipment includes this statement: "I am only selling these wonderful medium format cameras, because I have decided to go digital." Why do you suppose this is happening? Because the majority of photography does not need an image size greater than 11x14. And unless you are willing to drum-scan the medium format images, I feel the image quality of the digital image (properly interpolated) is, if not better, then at least comparable to a normally printed 120 negative or slide. I do not think you can achieve the same dynamic color or light range in the image with a normal film scanner that the D100 achieves, even at 4000 DPI with multipass scanning.
This is a very interesting and hotly contested issue, with a lot of emotion on both sides. Sadly (or happily) I still feel the pull of film. I suppose I always will. But, I have abandoned medium format in favor of digital. I have a few old Agfa Isolette 120 folders from the 1940's that I like to play with, but that's about it for MF. In 35mm, I only have my F5 left (I gave my N80 to my new son-in-law as a wedding present). I have thought over and over about selling my F5, but then I take it out of the bag and look at it, and I can't do it! I haven't shot more than a couple rolls of film in it since August of last year, since the day my D100 arrived. I have been captured by the D100. It is the first digital camera that truly works as good as or better than film (in my experience, anyway). I am now taking hundreds of pictures, where I used to only take a couple of rolls. I can experiment, and play, and approach my subject from 10 different angles. I see my images right now, so I can move to something new when satisfied.
Medium Format is not selling well. Many camera stores will no longer take MF trade-ins, since they have such a hard time moving the cameras. 35mm is still thriving, but, as they say in the Lord of The Rings, it will "diminish and go into the west."
Digital is here to stay now. In the next few years the cameras will improve, and get even more depth and capability, as does any great technology. The Foveon digital sensor chip looks very good to me, and there are others coming. Sell your MF equipment while people will still buy it, 'cause there ain't no going back! (as they say in Tennessee USA)
I will enjoy my D100, until the D200 is released, or the D2x. Then the craving will start all over again. Ten years from now, I will most likely still have my F5 AND the D100. I, like JRP (and many other Nikonians), am very sentimental over camera equipment that has captured small slices of my life. The D100 is a first, and at my age, I've learned to save those firsts. I wish I still had the original FM I bought in 1982, or even that little Fuji STX that I started 35mm with in 1979, or the Diana F I had in 1963. The images from all those cameras have captured the only look back in time I can take. All the people I know, some have died, others have aged, friends I haven't seen in years, but can see them anytime I please.
My Nikons have been my faithful companions, through many good and bad times. With my D100 I am increasing those memories I will have when I am old. And I'll leave original copies of each digital image with each of my six children. The real history of the world starts now. Digital is making it happen. Popular images will not degrade, rats and bugs won't eat the negatives, the sun won't fade them. 1000 years from now, people will be looking back at YOU with your images from your D100. Your great great great great grandkids will know you. Spread your images around. Give them to your family, friends, and even the neighbors. Your D100 will take you on into the future.