From what little I've seen of Larsen on TV, it seems like he needs time to develop feel for the game, especially a feel for how to rebound (not that he doesn't box out, he does, but he doesn't seem to have a natrual instinct to know where to be to get the ball).
But I would also guess that he would be very good, probably from day 1, at playing the Omar Williams role against the zone. That is, he has great size and seems to be a very good passer. At his size he can eat up space there and be a great target. Then, he is big and strong and skilled enough to find people in the seams against the zone at any angle.
Really, i think the only question with him is how long it takes him to adjust to the speed and timing of the college game in terms of rebounding and defense. At worst, I think he is comporable to a stronger, wider (though slightly shorter), at best he becomes Kevin Lyde.