Aoki's good at pure grappling, especially with a gi. He broke Hironaka's armbar in a swank manner in a pure grappling fight, which was cool. He also does some pure grappling matches on MMA shows (In the ring), which is cool. He tapped one guy with a freakin' gogo while he (Shinya) was on top. Yes, you read that right.
Aoki lost to the elite grapplers. He's no Marcelo, but he can succeed in pure grappling. He's a great MMA grappler, though, probably the best right now.