On the few times (2) that I did get to roll with him, I can tell you BJ's skills are out of this world. His knee ride/north south/side control pressure is of a 205+ lber. Very aggressive, and like most good black belts is 15-20 moves against you. Shinya Aoki is like that as well, with less strength, and more guard based. BJs top and bottom game is excellent, as are his hands. I would never stand with him. Power like crazy, good head movement, good footwork (cuts great angles). Not to mention he can stand in the pocket because he has a great chin.
Alas, his work ethic/drive is what kills him. Every now and then, he shows what he is capable of doing. (Gomi fight) I wish he were on Oahu more often, he is one of my favorite fighters because of his gifts. The only thing I don't like is his drive. Definitely one of the best (right up there with Fedor) when he wants to. Hopefully 07 we will see a rejuvenated Penn.