I've heard a few Fuzz Factory demos. I think it is a great fuzz pedal and ZVEX is a pro company but I am not sure it can get as nasty as the other pedals I mentioned. Correct me if I am wrong.
BTW here are some demo links:
YouTube - Bomber Boxx Germanium Fuzz Pedal YouTube - Dr. Scientist Frazz Dazzler.... a review YouTube - Mellowtone Wolf Computer Deluxe
Cheers!
Raff