I'd rather keep the color information in my raw files for maximum flexibility in the black and white conversion process. Having a monochrome camera would force me into using colored filters on my lenses again. That's okay with a rangefinder camera like a Leica MM (although a bit irritating at times switching filters), but it's really annoying to me with an SLR. I never liked looking through red, yellow, green, etc. filters when shooting black and white film in the past and wouldn't want to relive that experience with digital.