It's nice to be able to control so many permissions. However, a toolbar button is needed since it's kind of irritating to go to the addons manager and change permissions.
It would also be very nice if you could explain what would happen if a person blocks "Document, Dtd, Object,
ObjectSubRequest, Ping, Refresh, Stylesheet, Subdocument, Xbl,XmlHttpRequest" for a particular site (You've also mentioned that some of these content types are not supported by Firefox.
Please explain. Thanks!