From the few bands I have heard that have female growlers, like Arch Enemy, Holy Moses, Gallhammer, and The Agonist, I think they are pretty okay. They have a certain sound to their voice that male vocalists don't, and I kind like that extra texture they bring. I love seeing women in metal, and I really want there to be more, since rock as a whole seems to have a chronic lack of females. Diversity ftw. 