One very strong advantage to me is being able to see the subject at the exact moment of exposure, i.e. if he blinked. I don't know too many people who use an accessory finder in the flash shoe of a DSLR, but that would work too.
Like a lot of people who use an M8, I use a DSLR too. In my case it's an "ancient" Canon 20D, not even a 5D. I've said a few times, to the chagrin of a few enthusiastic M8 fans, that in terms of image quality I don't see the 20D lagging behind the M8 once the RAW files are properly processed and printed. To me, comparing RAW files is like tasting raw meat: what matters is how they taste once they're seasoned and cooked. I'm sure the files from a 5D, IDS-MkII or III, 5D-II, or the Nikon full-framers, are even better in most respects than my 20D, but I have no interest (and fortunately, no need) to cart them and their bazooka lenses around. Been there, done that. Were it not for the M8, I would most likely be shooting a Canon G10 right now, so that's what I need to compare to. In that case (and with all due respect to the G10 which is a remarkably competent image-maker) I'll take the image quality of the M8, as well as just about everything else about the M8.