I guess I can't say I'm really a prospective M8 buyer unless I sell one of my cars (which I'm seriously considering!) Then again, given that some observers are predicting a one-year backlog, I may have been able to save up enough money by the time they're readily available at retail!
However, I'd like to answer based on the experience I've already gone through when I got my R-D 1:
1) I had fully expected to continue to shoot film. I liked my film cameras, I had all the equipment I needed to work with film, I enjoyed the process of developing and printing, and I knew from experience that for hang-on-the-wall prints, it was easier for me to get the subtleties I wanted with a wet print than with an inkjet print.
And yet... the fact is that during the past year and a half I have shot a total of two rolls of film, and one of them was just to test a camera I was going to put up for sale on eBay. I still feel something is missing from my photography because I don't use film. In fact, I feel like a traitor for not using more film. But the fact is that the results I get with the R-D 1 fufill all my needs (and the needs of people for whom I take pictures.)
And I learned that no matter how good my intentions, there just didn't seem to be enough time to do a good job of being a film photographer and of being a digital photographer. I'm still not quite sure how this happened, but it did. My theory is that any given person has a certain level of commitment to photography: ignoring the issue of what it is or how to measure it, let's just call it X.
For any given commitment level X, you'll need to invest a certain amount of time, money, energy and effort. What I've learned is that X is exactly the same whether you're photographing digitally or conventionally.
If you wanted to be equally committed to conventional and digital photography, your commitment level would have to jump to 2X, and for me there just wasn't enough spare time, money, energy and effort to make that possible.
2) Yes, I'm already using the R-D 1, a Nikon D100 (probably to be replaced sometime with a D80), and a Canon D60 and a Fuji GX680 with digital back at work.
I started out with various Olympus digital point-and-shoots (which surprised me with how well they worked even for fairly serious snapshots) and then got the D100 (which works well, but which I dislike basically because it's an SLR and I hate using SLRs.) It wasn't until I got the R-D 1 that I was able to really buy into the idea of digital photography, but now I'm convinced that I can do good work that way.
3) The 1.5x "crop factor" of the D100 and later the R-D 1 made me think at first that I'd need to rethink my lens choices. But I discovered that wasn't the case. After I got used to it, I just didn't worry about it at all. In general, I tend to use a 50mm lens in the same types of situations for which I'd have used a 50mm lens on a film camera; ditto a 35; ditto a 28, etc. (I did buy a 21mm lens to use on the R-D 1, but very seldom use it. I'm not a super-wide-angle kind of guy.)
This was counterintuitive and surprised me a bit. But I realized that since I had always done my own developing and printing with film, I was used to shooting a bit "loose" (to accommodate fast-action situations) and then cropping the negs down to my desired composition in the darkroom. Shooting digital just meant I was shooting a bit "tighter," so it really wasn't that big an adjustment.
4) I'm already 'way deep into digital stuff, including image management and printing. I've got an Epson R800 pigment printer and keep thinking I should buy a larger printer so I can make more hang-on-the-wall prints.
But again, the surprise is that I don't really have a need or demand to make a lot of prints. When I take pictures for other people, I edit them, put them on my web server, and let them view or download them from there. I usually post 1800x1200-pixel images so they could upload them to Walgreen's or whatever and get good 4x6 prints... but surprisingly, people tell me they almost never do. Lots of people, especially younger people, are perfectly happy viewing pictures solely on their computers.
For those who don't, there's another option: Fairly recently I've gotten involved in using a piece of software called Photo to Movie to turn my picture collections from performances, concerts, events, etc. into motion-graphic "slide shows," with titles and effects etc., which I then burn onto DVDs with my Mac. The DVDs play in any TV-type DVD player, and the images look great on a TV. Most everybody I know has a DVD player, and they just love these DVDs. And they're so cheap to make that I can just give them away to anybody who wants one (although I suppose I should start selling them if I want to raise enough money to buy an M8!)
So, this answer has run a bit longer than probably you wanted or than I had intended. But I wanted to point out to digital newcomers who may be brought in by the M8 that "going digital" may change a lot more than just what type of camera you use! You may find that you still take pictures almost exactly the same way you did with film, but that you now edit, store, manage, view and distribute them differently.
I'm still ambivalent about that -- sometimes I look at the Agfa Portriga-Rapid prints I have on my walls and feel, "Well, I'll never be able to do anything like that again." But I wouldn't be able to anyway, since Portriga-Rapid has been discontinued for years, and so now I'm just trying to go with the flow of what seems to work in my photo-life...