Well, first post here, and I haven't read all the thread (not that much time!) but since it's a poll...
I'm on the waiting list for an M8 and have put some money down already. I don't think I've ever been as excited by a camera as this one.
The biggest thing for me will be to see high ISO files. If they're as good as Leica is claiming, they will have a winner on their hands.
Why? Well, I own a Canon 1ds2 and a Leica R9 / DMR. The Canon is rock solid, for sure and a truly wonderful camera, but it's being sold. I will miss full-frame, yes, but for now that's not as important to me as the output.
The DMR and the 16bit sensor just makes prints I like better, without nearly as much PS work. It's that simple. Yes, I know how to tweak the 1 series output, but trust me, the DMR files end up being better prints. (And no, you *can't* make a 50 1.4 Canon lens look like a 50 1.4 Summilux in Photoshop. Sorry. Just shoot somebody's face who's strongly backlit, and you'll see exactly what I mean.)
So the DMR wins, and I expect the M8 to be even betteer. Well, except for noise... You need to nail the exposure with the DMR; it's not as forgiving as the Canon in terms of exposure--not at all. And noise plays a big role in that. The Canon is wonderfully noiseless when the DMR gives out entirely.
So if the M8--optimised for C1, ISO 2500, M glass--delivers on the image quality at high speed, I think it will be a relatively big hit for Leica. I like SLRs, but as a pro I also need a rangefinder: something small and really unobtrusive and uncompromising in terms of quality.
BTW--I just read here that someone thinks the DOF scale on Leica lenses is all wrong for digital? Well, it is, but on the newer lenses, anyway, the smaller sensor actually increases the effective DOF, so when you're street shooting, this is mostly a plus, not a minus.
Of course, now I only need to see what Canon announces at Photokina.