Using half colour filters with B&W film?

I was surfing the Scheinder [aka B&W] website awhile back and noticed a comment about using those graduated colour filters with B&W film. Anybody try it? It would seem a nice idea. Use a red or orange filter to get the sky right without darkening everything else. The filters are designed for colour use so I guess I'll need to look at what light they pass but any other issues people can see?

I know B&W is in the business of selling filters so I naturally assume they're too positive on the process-)

The practical issue with grads, Nick, is uneven horizon lines. I always seem to end up with a mountain or something poking up into the grad area.

I haven't seen a real mountain in years-( Have to think about it some more. I've asked B&W for some more info on the things maybe that will push me one or the other.