Oddly enough even though I like his swing it's so fast he has very little bat control. He needs to work on making contact first. Then look for power and pulling the ball.
I will say another thing. With his swing when it comes together he is going to be really good. His swing isn't quite as nice as Ken Griffey, Jr. But it's close.
I just watched a bunch of his at bats. His mechanics look fine. I think it's pitch recognition and the off speed pitches that are the 2 issues. Only repetition can solve those problems.