It seems that Categories need to be further integrated into Radio.  It seems the only thing they allow you to do is post separate bliogs to it and create a separate News feed/xml file.   They DO NOT,  as far as I have experienced it or understood as of yet:   Thery don’t allow you to send mail that posts to them……they don’t give you an index.html page like the Stories list does,  and they don’t ,  as someone else here pointed out,  have a separate stories list for each category.