I've rolled with him.
Keep in mind I've rolled with Rafael Mendes, Cobrinha, Cyborg, Cavaca, Marcelo Garcia, Pimenta, Rodolfo Vieira etc., etc...and I remain to this day impressed with him and consider him one of the top grapplers I've rolled with (don't ask me to do a numerical list cause it won't happen).
First I'd like to point out how much of a gentleman he was about it. Kirik (owner of the UG) took me on a New England training trek two summers ago if I'd blog about it for the UG. He knows John and took me to Renzo's, telling me to make sure I mention I'm Kirik's friend and to ask kindly if I could roll. I did this and he said, "I really can't, I've got a private lesson right now I'm already a little late for...wait, where are you from?" "Arkansas." "How long are you here?" "Just today." And he changed his mind and took the time to roll with me, little unknown purple belt.
He isn't physically dominating at all. He's one of the smoothest people I've ever rolled with. He didn't force a single thing he just moved six steps ahead of me. I was fascinated and frustrated. He had put so much time and thinking into it that it seemed like he was one of those cutting horses and I was the calf...every flinch of my muscle, any glance, and he knew where I was heading and would beat me to it. Amazing.
Now, of course, I'm a girl and I was a purple belt. But I watched his lesson--that was with a black belt--and he did the same thing. This isn't a nobody black belt, it's someone with a name, and he appeared to be just playing. Very, very, very impressed. He's a VERY intelligent grappler.