I think one area that he needs to work on is on rebounding. He doesn't position himself very well to get offensive or defensive rebounds. I think that is one area that Kanter is pretty good at. I also noticed a few times where he was late on switching.
However, as others said, those are all areas that he can work on. I think the improvement we are seeing is great. Right now, I think he is looking like a McGee type of player. An athletic big with lobbying power and finishes well under the rim. However, with his progression, I think he can develop even further. If he would bulk up, then he could become a Dwight Howard (in terms of ability, not passion for game).