[Let's see if this spoiler tag thing works.]I liked Hawkeye's scary competence but was a little surprised that he spent about half the film under mind control. Thor was cool but not really my favourite, although Stark's Shakespeare insults were hilarious. Coulson... *sigh* To be honest, I wasn't even sad, just disappointed. Seriously Joss, when the deaths are this predictable, it doesn't enhance your writing, it just makes it tired. You don't have a freaking quota to fill; just knock it off. It's not like it was even necessary; we all know how manipulative Fury can be. To be honest, he might still be, and Coulson's stashed away somewhere undergoing an exciting new superhero procedure. I'd welcome it, frankly. It'd be interesting seeing him as an Avenger.
I appreciated Natasha's cool capability, and it was nice seeing Pepper again. Hulk managed to be hilarious while totally showing people why you should be scared of him. His smackdown of Loki mid-pretentious speech had the whole cinema laughing :-).
I'm not sure whether I really care about the sequel villain reveal at the end, I've never been particularly enamored of Thanos. I have to admit though, Joss's script there was pretty genius. Paraphrased:
Evil minion: OMG, we totally can't go to Earth, Master, it would be courting death!!!
*Thanos perks up*
Evil minion: ...shit.
Hilarious because it's ominous for those that don't read the comics, but those that do, and know of Thanos's... romantic inclinations totally got the other side of it :-).