Batum is a solid all-around basketball player who still has plenty of time and room to improve. When his outside shot falls he's incredibly valuable, and his ability to make plays off the dribble adds an important dimension to Batum's attack.
That doesn't mean Charlotte was right to trade Vonleh for him, but if they make the playoffs this season it'll be worth it.
The mark of a great NBA offense is the ability to respond to openings quickly and competently from every position. Batum embodies that ideal. He exists not to create breakdowns but to exploit them; once a teammate collapses the defense with a drive or forces overreaction on a post-up, the ball works through Batum to find its most effective endpoint. Sometimes it lies with him. Batum had a rough shooting season last year but has otherwise been a reliable spot-up choice. Slashing against a rotating defense is a comfortable act for him, too, as Batum has no problem putting the ball on the floor and navigating his way around scrambling defenders.