So I've had a few thoughts, but mostly I've just worked through what makes the Hulk tick. Consider this an all-purpose Avengers discussion post; feel free to bring up other topics. This is just all I got right now because, as my icon indicates, I am tired. Also, I wrote it a bit dis-jointedly in between reading stuff online.
After reading TV Tropes:
Bruce Banner is always angry. That means he's been practicing self-control, not emotional control. The Hulk is part of who he is-it's his base emotions cranked up to eleven. Which means that the issue is not the Hulk being an uncontrollable smashing machine, it's that BB is angry at and afraid of himself, and completely rejecting a lot of the things that make him who he is. Especially given that the times he does lose control, he's EXTREMELY angry or afraid, and the Hulk reflects those feelings. Add to that the fact that everyone around the Hulk is terrified of him and trying to fight and stop him, and you get a rampage. BB didn't realize how much the Hulk was him until he learned that the Hulk deliberately aimed to crashland on an abandoned factory to avoid hurting people. He accepted it, and the next time he became the Hulk he did so voluntarily, which made a huge difference in how controllable he was. Because instead of emerging in a blind rage with the whole world out to get him, including himself, BB essentially asked for help, and he emerged calmly among people who wanted him there and weren't trying to hurt him.
After reading Gamers With Jobs:
Tempers were already running high the first time, and the attack was the last straw. He lost control, and he actually was specifically angry at Black Widow because she was the one who got him into the mess. Everyone else in that scene attacked him first.
And BB is the one with the rage problems...
(quoting now)
“Think of the Hulk as a schizophrenic. The man with two brains.
Tony's take is that Banner is the source of the pathology, not the Hulk. Banner hides behind that excuse. The reality is that he has been forcing himself to become Banner. His natural state is as the Hulk. The day he no longer decides to become Banner, is the day the Hulk finally is cured of his schizophrenia. His inner turmoil and bouts of uncontrollable rage will end.
The Hulk is not inherently evil. He is not rage personified. Banner is. He is a clenched fist all the time. It is Banner's fault that the Hulk is a giant green rage monster, not the Hulk's.
Greatest nerd rage story ever.
FanTAStic. Banner as the one who's out of control; I love it. The Hulk runs amok (or at least seems to) because the only time he gets to be himself is when Banner totally loses it.
The reason why Banner wants to 'stay calm' all the time is, of course, because society looks very negatively on people who aren't. He feels like, in order to fit in, he has to be cool and collected, even though he's seething.
The Hulk, of course, just likes smashing things.”
My conclusion: Rage is not the real trigger. The Hulk is not his anger personified. It's just that, at first, and when he's not careful, blind rage or near-death adrenaline is what pushes the switch, so those emotions get cranked up to eleven because that's what he is feeling at the time. BB has an awful, awful temper, but he's spent so much time and effort not expressing it that it builds up to a breaking point, something goes snap, and he lets the world know what he really thinks.
And it's worse than that, because after the lab accident and becoming the Hulk, he blames his temper on the Hulk and fights with it-with himself-rather than dealing with it. He's learned how to not pull the trigger for ordinary everyday anger, but he's also focusing all his frustration and hatred of the situation on 'the other guy', which makes him exceptionally pissed off when he does mistakenly pull the trigger.
In the battle at the end, he pulls the trigger deliberately, after realizing that the Hulk is actually the same guy, and he's much easier to deal with because he didn't lose control, he's not angry with himself for losing control, he's not especially angry at anyone other than probably Loki.
...that's my take, anyway.