Ash, thanks for the feedback. I was experimenting with stripping out the digital "punch" in color, so in that respect it worked. I agree the loss in saturation in the B&W areas caused by revealing the masked colors is a problem; probably needs another layer to bring that saturation back. After playing around with it some more, however, I don't really like the effect all that much and will probably push on to something else. I even pushed it further and came up with this image.
I think we're in agreement here, the technique seems neither fish nor fowl. Thanks, once again your responses are informed and helpful,
Brian