I didn't read the book so i skip that part, sorry (still hoping here that i'll manage to read it and don't want to be spoiled).

I actually agree with youor view of lead character of Hurt locker. I even think we as viewers weren't supposed to like him (at least at first). For me it was a story not about liking a character but aboout understanding him. Does it have a sense?
You said it right - he's junkie and his dangerous that way. I think the narration in the beginning of the movie told the same thing. In the end i was hoping that it was just a part of his life and maybe in the future he'll meet someone who will teach him how to cope. it's strange actually, i didn't like a character but i felt for him. Usually if i don't like someone on screen i feel nothing for them. I think that was a lesson of that movie (at least for me)and why it was praised so much. it grabs you even if you don't like a character it tells its story through.
Oh, and i think the lead actor (don't remember his name, sorry) did a very good job portraying Will.