Rated 4 out of 5 stars
As Jaker788 mentioned, this is currently broken in Firefox/Aurora 8.0. I looked at the support site (a forum on Userscripts.org), but that doesn't appear to be monitored any longer. The last post in the update thread was several months old, and the forum is filled with spam posts.
It's possible (though I hope not) that development may have stopped on this extension. It hasn't been updated since before Fx 5.0 was released.
This is a great addon, but not a critical one. I hope the developer updates it, but if he doesn't (for whatever reason), it won't be the end of the world.