I'm a KU fan so I have seen Mclemore play alot and know his game very well, but I have my concerns. He has all kinds of talent, but he has a demeanor that scares me. He just flat out isn't very aggressive, and I could imagine he would be even more passive in the NBA since he will be playing on a whole new level with superstars and veterans, which I'm sure would be intimidating. And to be fair, it could maybe be used in a good way since it shows he isn't selfish and can learn to play within the flow of an offense which is a great trait to have, but there were SO many times where he should have taken over on KU and be more aggressive to lead his team to victory, but he never really did and let his far less superior teammates continue to make the plays. That shows lack of leadership to me, which can be learned, but the guy has to be way more aggressive and hopefully he can figure it out in the NBA.
That being said, I think he will be a solid player in the league and won't be a bust by any stretch, but I don't think he will live up to the hype and expectation that everyone has for him. He definitely has the potential to be a player like Ray Allen in his prime, but I don't think he will quite get there but could get close. So that said, would a player that could potentially be Ray Allen at the best be super worth a number one pick? Not really in my opinion, especially when we have Dion who will either be just as good of a player, if not better. And I highly doubt Dion would want to come off the bench, especially to a rookie. So basically I'm not sure he fits either way.
I would only take him if Nerlens had confirmed injury complications, but even then you would have to consider other candidates.