Refreshed after a good night's sleep what to make of the Leica M-Monochrom? Essentially an M9 body, with all it's strengths and weaknesses, with a black and white sensor which offers pin sharp resolution, less noise and the opportunity for higher ISO will appeal to the Leica guys and gals who regularly discard the colour information anyway.
The elephant in the room is the M10. If the output from the M10 were converted to black and white how close would the IQ get to that of the Monochrom? Hard to say, particularly as the M10 hasn't even been announced, but my guess is that if Leica are able to deploy a class leading sensor the difference would be irrelevant for all but the most demanding work. And the M10 would also offer the ability to correct chromatic aberration, something that isn't possible using a monochrome sensor. Chromatic aberration may not be much of an issue with most Leica glass (I've not read enough reviews to know) but there doesn't have to be much present at the corners of an image to wipe out any gains that a monochrome sensor can claim in terms of increased resolution because it lacks a colour sensor's Bayer matrix. Guesswork on my part so take your own view on that.
One would also expect an M10 to feature other improvements. The specialist forums are full of suggestions and almost equally full of denials that such improvements are needed (LED illuminated frame lines, focus confirmation, an improved rear LCD and behind the scenes firmware/hardware improvements) but, however it turns out, Leica know their customers and I'm sure the M10 body will be another step up from the M9.
The bottom line is that if I won the lottery I'd want both an M-Monochrom and an M10 just because I could. But if forced to choose just one body then I'd wait a few months and, if my guesswork is correct, buy an M10. The M9 already offers options for Black+White and Vintage B&W shooting and I have a feeling that the M10 may come very close to the M-Monochrom in those modes and it, the M10, will also be able to do colour and have the advantages of a next generation body. A no-brainer, so far as I'm concerned, but that's assuming I have a working brain in the first place!
Just a thought. Sorry Leica.