[boost] A Refcounting Handle Class that supports CrossCasts

I have developed a nonintrusive Reference Counting Handle class that supports crosscasts. The limitaions are that both source and target parameter types must have virtual methods, and that currently it don't supports access from multiple threads, Do the esteemed members of this list think that such a class would be a useful addition to the library?? "Home is not where you are born, but where your heart finds peace" - Tommy Nordgren, "The dying old crone"