Thoughts on Leica M Monochrom???

I shoot Sigma SD15 and SD10 when I want to shoot digital, B&W, lately my old Pentax K2000 in monochrome mode, not a true monochrome sensor, none are, but with a bit of post to clean up the noise and tweak the contrast petty good for cameras that cost just a few hundred. I use digital black and white for travel now that the airports scanners can fry film. I'm sure the Leica will out perform my Sigma, but for $3000 for a used Leica, I can live with that.