LOL.. it's no secret he wasn't very good at PITT. He was still adjusting to the College level of play in the US. He said as much in his interview. But he is a legit 7 footer. He has proven to be an instinctive shot blocker. He runs the floors and finish dunks. Plus, he has proven at the Combine that his shooting has improved massively, he was one of the best shooters there (mid range).
Big men develops slowly (see Ibaka/Marc Gasol), but looking at the "tools" he has right now, together with his heady-ness, fight, and willingness to improve, I'm projecting him to be a solid future pro - a legit 7 foot, shot blocker who shoots the 12 footer consistently. Sounds like a perfect 3rd big to me.