When I was at Whitby Folk Week in the UK in August, I was amazed at how well-known Mudcat was in the UK. It seems that Mudcat may have almost universal recognition among UK folkies.
Not so in the U.S., but a lot of what is called "folk" in the U.S. is certainly not "traditional."
And no, I don't think Mudcat really addresses the interests of bluegrass or old-timey enthusiasts, or of the singer-songwriter fans. Maybe that's just as well.
-Joe Offer-