Having owned him in my hockey pool for a few years now, I've watched him quite a bit. He's the kind of player you watch and think, "this guy could be as productive as anyone", yet for his talent, his name doesn't show up on the scoresheet very often. Much of that is because Anaheim is just a black hole of offense, but part of it is that he has no control over his massive shot. He tries to pick corners, but he's the sort of player who should just aim for the center of the net... since he's bound to be off by two feet and that should land the puck in a corner half the time.
I really, really like his potential; he's quick and dynamic... if he can put it all together on the right team, he could be a 50-60 point defenseman. Is Buffalo that team? I'd guess not, since they have the finest young D-man in the league already, and I imagine he'll be relegated to the 2nd power play once again. He deserves a shot on the 1st power play of a decent team, and he'd probably be dynamite together with Dahlin, but I'd guess Buffalo already has a setup they're pretty comfortable with.
One important thing to know about Montour is that he's a late-bloomer. He didn't start taking hockey seriously until late in his teens... lacrosse was his sport, and presumably that changed when he realized only lacrosse players care about lacrosse. Basically, he's like a typical 21 year-old in his development, with plenty of room to grow. And this shows, because over the last year, his presence in his own zone has improved dramatically. If the improvement over the last year could continue for a couple more, you'll have a very special player on your hands... if he can just remember the great Howie Meeker's advice: "you gotta hit the net!".