He's either going to boom or bust. That's all I got.
From the few games I've seen him in...he seems to have a heart of a lion/winner, great attitude (team player), very very feisty on ice (good for lots of garbage goals), and bonus part...always smiling! (seems like a good kid). Size? Not worried about size as long as he has a huge heart. Some players are 6'2 or 6'3 but have zero heart.
Some comparisons? (or wishful thinking):
Steve Sullivan, Gionta, a more gritty/feisty Samsonov...and I like the Ferraro comparison. Maybe Gallagher can be a mini-Theoren Fleury? (I'm allowed to dream!).
A mini-Fleury? Is Gallagher 5'2" or something?
But I do see some good feisty qualities to his game. If he can fill out some more, I think he could be very effective.
He's pretty feisty and always around the net. The latter part reminds of Gionta. I haven't seen him shoot enough yet to know if he could score quite as much as Gionta, though. He always seems to be doing short-distance stuff and charging in for garbage and rebounds. Very small to be doing that against NHL defense size and strength, of course, but he seems to be resilient.
If he can score 20 one day and get his skating up to the point where he is effective defensively and at agitating in all zones, not just the goal crease scrambles, then he'll be quite an effective player.
He should top Gionta...Gallgher scored 20 points in 36 games in AHL, as 20 year old. Gionta scored 25 points in 37 games his first year in AHL. But as 23 year old.