Was Han's short-tempered demeanor in this film intentional or was it just one of those "throw it in" type of things? I feel like his hot-headed vibe/behavior is very noticeable from when we first see him at the start of the film - oddly enough, he seems to be a lot more mellow in the Bespin scenes when he is detained/tortured by Vader and his men.
Thoughts?
In the first film he's just sort of being dragged along in the wake of the Jedi, he didn't plan for any of that shit and for most of the film is uncommitted to anything except defending himself and paying his debts. In the second film, he's in DEEP! He's deeply committed to Leia and the Rebel cause, and to his best pal Luke the Jedi, they're all in peril and he's got to do whatever he can to save them. He can't sit back and comment on the action this time, he's got to give the events of TESB everything he's got, respond to each new crisis with every bit of courage and commitment and crazy improvisation in his being, and Ford rightly played the role with a lot more emotional intensity.
It was only in the 3rd film that his performance went to hell, and he started to look visibly bored with the role.