I have liked what I have seen from him in summer league play. I see an NBA level athlete that has not developed the skill or touch necessary for the NBA. I have not seen any of the Euro games and hardly any of the highlights. But think of it this way, say he was on Duke and put up 28 points against North Carolina at 20 years old. I think that would be viewed that he is a top college player and a player that is on track to go high in the draft.
It is really hard to gauge players in the Euro leagues, especially young ones. They are playing against men, more physically developed men then is seen in the NCAA. But that doesn't mean anything any more than some players have great college success but then do nothing in the NBA. Begarin has to developed skill and touch. I always have seen him as a guard but at 6'-5", maybe he can be a forward.
He will be 21 for next season. That is probably when he will need to be ready for the NBA if it is going to happen. Not absolutely the last chance for him but definitely the point where you would expect to start to see the NBA talent if it is there.