Hulk is a decent player, he's quick, and strong (as you'd guess by his nickname). He's a decent dribbler, not tricky like AJ or Silva, but more a powerful runner with the ball. I would say not to dissimilar to Yaya and Anelka the way he dribbles: beats people with pace, but not out of control.
His main asset is his left foot, he strikes a good ball and is also a fairly decent crosser. He works pretty hard and seems to have a decent attitude.
From what I saw of Porto this year, Falcao is a better finisher, but Hulk has more about him. He's not as cultured as Aguero, but maybe more suited to the EPL. I would take him in a heart beat. He seems like a Mancini type player too, and offers flexibility as he can play up top or from either wing.
From what he says in the press he seems like quite a loyal guy, I'm not sure how that affects us. If he leaves this year he will go against what he has said so far, I expect him to leave Porto next year.
EDIT: Also he looks like he'd be pretty good in a fight! Which is never a bad thing