I will consider a mirrorless when it does not cost 4x the price of the equivalent DSLR and it mounts Nikon F lenses.
Sound some better samples of M246 around. Maybe I was a bit too skeptical :P
I looked and saw nothing special. My father's candid photos taken in an Olympus Trip 35 looked better. Perhaps the M photos printed in a high-contrast paper would finally please me... I don't know.
B&W pictures need filtering to be good. Either you have a monochrome camera and a bag of filters, or you use the DSLR you have and do the filtering at will in the computer. I prefer the second option.