For starters, he's young and a bit raw. LSU used a lot of defensive line rotations, so he's limited in his technique and experience, but supposedly has an incredible work ethic and is considered stellar teammate and leader, plus plays with a a high motor.
I don't think he's anywhere close to hitting his max potential, yet, and flashes the ability to disrupt like other first round defensive tackles in this draft, yet can be driven out of plays too often. He played at 295 pounds last year, but it was obvious he can handle more weight on his frame, and proved that weighing in at 309 at the combine. He can probably keep adding to the total, as well.
IMO, he's got a bright future as an every down, do it all type defensive tackle if he's allowed to grow into the role, but I'm not sure he's ready to step in as a 2-down run-stuffer Day 1.
Draft stock-wise, I think late 3rd is his floor where he can play as a situational pass-rusher, but some teams may want to play him early and ride out his growing pains, so maybe drafting him late 2nd, early 3rd.
"People who don't punch their ponies in the face make me sick." - Louis C.K.