Colin, at the time of the M8 (2006 aug/sept) there was a faint rumour going around Leica regarding the making of a dedictaed bl/w version (12-15 Mp). I decided to hold off and wait for that. Of course, they later cancelled the idea, at least for the time being. In general I like the camera, some beefs with the ergonomics (too slippery covering, a bit noisy advance, but image quality was and is top notch.
I have discovered that I am at heart an "analog" shooter. To many decades with fingers in developers and the fumes of various chemicals probably is to blame.
However, if I today had to go back and earn a living as a photographer, I would go digital all the way! Probably Nikon D3's and a M8/Rd1 and every concivable gadget available!!
I think that some of the bad press the M8 has been given is more user ignorance than anything. There were problems with the camera, but none were insurmountable (except the "sudden death" syndrome, that afflicted some). It was probably pushed through a bit too fast, but it also saved the company.
IF someone comes out with a full frame 12-16 MP rangefinder, with a M-mount and a dedicated bl/w mode (not a RAW converted one) and at price that was reasonable ($3500-4000 max) I would go for it. It would be a complementary camera to my M's, probably never my "main" camera.
I do have a digital, a Ricoh GRD which is set on "monochrome" mode and I use it as a notebook and for extreme cose-ups. It is simple, but very good and the fact that you can go down to 1.5 cm in macromode is great for getting a shot of a lens detail or a serial number!
Ergonomiccally I prefered the RD 1 to the M8. The advance lever gave you a nice spot to rest your thumb, the screen could be flipped inward and the camera used as a "camera" without looking at the screen every shot! It also protected the screen from scatches etc without resorting to exotic and expensive glass as an extra cost!