Rob, the Monochrom come REALLY close to an M6 and film. The only issue it has, in my test of the camera, is how the highlights clip. It clips to white very abruptly, doesn't have that film haliation look to blown highlights.
My ultimate conclusion is that the D800 can produce comparable B&W, but then again, the D800 is a bit bigger than an M, and of course the lenses are different. The M (240) has a nice file, as well.
I would rather shoot film, but for various reasons I can't make wet prints, and decent scans of 35mm require a very good scanner. I ran the numbers and realized that getting a Mono costs a little more than getting a good scanner and another M6, and I don't have to scan, so . . .
Now that I have a job I don't have the time to spend scanning and processing film. I can do medium format on my Epson V750, for smaller prints, but 35mm is another deal entirely.