Webster just has a great feel for putting the ball in the basket at the high school level, especially from the perimeter. Part of this is due to the fact that he's so much more mature than most players his age both physically (much bigger and stronger than anyone at his position) and mentally, but the fact that he is a very skilled player who has a good feel for the game can not be ignored.
Webster is a very natural shooter with excellent mechanics and nice elevation on his jump shot, although his release is a bit on the slow side because of his very deliberate motions. Once he sets his feet and gets his shoulders square, though, he is lights out. He can hit his jumper from anywhere on the court, and is good at getting his shot off in tough situations.
Physically, he's got a great body that is certainly ready for the NBA, and an above average wingspan. These skills make him an above average rebounder for the swing positions, because he can simply out-muscle his fellow guards for rebounds. And of course, his leaping ability also helps in this regard as he is quick to rise.
His playing style is pretty unique, and that's probably why so many people are intrigued by his game. He is most definitely not explosive, but has a certain smoothness to him, combined with good court awareness, maturity and an understanding of what's going on around him. In transition, he has powerful long strides, which are deliberate, but help him get to the basket and then finish strong. He shows a willingness to play within a set offense, not forcing the issue too much compared with most players his age (all-star games aside) and appearing to understand his role.
In terms of his intangibles, they appear to be fairly strong. His court demeanor looks good, he interacts well with his teammates and he seems to be a well spoken kid. He plays unselfishly and appears to be pretty mature for his age while carrying himself well on the court. He also supposedly has a very good work ethic.
Something that hurts his potential to develop from a high school standout into an NBA star is that fact that his athletic ability is fairly underwhelming. He is not a stiff by any means, but is also not quick or explosive at all either. Webster's slashing ability suffers greatly because of this, as he already does not have great ball-handling skills (he only seems to go left) and combined with his average first step, this hurts his scoring potential. Watching tapes of his from high school, players his age don't seem to have too much trouble staying in front of him, although he does a pretty good job at masking this weakness by not forcing the issue too much.
Webster's footwork needs serious work on both ends of the court, especially since his feet aren't the quickest. He can come off a screen very well and elevate for a beautiful jump shot in rhythm or off one dribble, but anything more than that isn't quite there yet on a consistent basis. His off the ball movement could use some work as well.
All of this is meant to diversify his offensive approach to the game, which is sorely needed. Right now the only NBA ready skills he has on the offensive end is his ability to hit a set shot (which is impressive). However, he doesn't move that well without the ball, he cannot create that well off the dribble, he rarely plays in the post (even against weaker defenders), and he has not shown any ability in terms of creating for other players.
Defensively, his lateral quickness is extremely poor, and he'll very likely be a defensive liability for his first couple of seasons guarding NBA shooting guards until he learns how to adapt himself. Webster puts in the effort on the defensive end, but he just doesn't have the quickness or footwork to keep up with the athletic swingmen types he matches up with at the high school level. Playing as a professional, this problem will only be much worse.
While he has a great body, Webster doesn't really take advantage of it that much, which makes you wonder how useful it is.
Webster is a player who has shown a few intriguing skills as far as the NBA is concerned, especially his jump shot. The rest of his game will be decided by his upside, which at the moment is unknown. NBA teams appear to be willing to give him the benefit of the doubt in this area, though, because all high school prospects are supposed to have unlimited potential when they declare for the draft. Webster has his work cut out in many areas of the game to show that he is not just a one-dimensional shooter and that his lack of athleticism does not hurt his ability to develop the rest of his game.
Webster has already hired an agent, so he is in the draft for good. He is considered by some to be the 2nd or 3rd best high school player in this draft. It has almost become a foregone conclusion that he will be drafted high because of the success of previous high school classes, especially last years. We'll have to see how that plays out, because he certainly isn't your typical high school prospect when you compare him to players his size from last year's high school class for example (Shaun Livingston, Josh Smith, JR Smith, Dorell Wright).