Went to see it last Thursday, and I thought I'd better finish my review entry and post it as all you US-ians are getting your midnight showings in.
The non-spoilery reaction: I really enjoyed it! It was a big, goofy team-up comic translated to the big screen, with all the best and worst that implies. Not very cerebral even by the lofty standards of superhero movies, but juuuuust enough heart to carry you through to the end, and excellent action sequences. Also quips, lots of quips. Seriously, if you don’t like or at least tolerate Whedonisms, don’t even bother going because you will be gnawing your arm off half an hour in.
The action was definitely the strongest part of the movie. The stunts were exciting and the CGI was convincing, making the Chitauri army (or at least those giant space-whale things) genuinely intimidating. I got a fairly good sense of what was going on with the battle as a whole while still feeling like I was in the thick of the fight (assuming I would be in the middle of a superhero fight without running away screaming, that is). If there was a weakness to the action it's that it went on just a smidge too long and had a few too many climaxes. I was definitely feeling Action Scene Fatigue before events started revving up towards the ending. But not nearly enough to impinge on my overall enjoyment.
Character/storywise ... well, with six title characters, one drama-hogging villain and several important tertiary characters to juggle, there's only so much screentime to go around. With the possible exceptions of Loki and Black Widow (see below) I don't think anyone who hasn't seen at least one or two of the previous films would find the cast of this one particularly memorable. That said, I have to give Whedon credit for being able to juggle a large cast while giving everyone their moment in the spotlight. An arguable exception is Hawkeye, who was sidelined for the first 2/3rds of the film for Plot Reasons but made up for lost time -- if anyone ever asks me how a guy who shoots arrows can hold his own on a team with a thunder god, a man in a flying armored powersuit, and a superpowered giant, I can just show them his fight scenes in this film and we're good.
On the other hand, there was Coulson, who had a couple of shining scenes -- one with Pepper Potts, which was one of my favorite moments in the film, and one versus Loki -- and then died. Which was predictable in retrospect, given both Whedeon's propensities and narrative tradition, but took me by surprise after all his guest appearances and crossings-over into the cartoons and the mainstream Marvel universe. Huh. Actually, "huh" about sums up the problem -- despite having seen all the previous MCU films and enjoyed all of Coulson's own shorts, after a pang of sadness his death just made me feel underwhelmed, and worse, unconvinced that his death in particular could galvanise the Avengers into a real team with a real purpose. Unlike, what, all the other people who died in that same attack? Sure, they'd all met him a few times, but it still felt forced.
As I said above, though, Loki and Black Widow were the standout characters. I was a little worried that the nuanced Loki of Thor would become your average hammy villain in The Avengers. I don't know whether it's Whedon's writing or that Hiddleston has a firmer grasp on the character, but I actually found him a better character in the newer film than the older. As much as I enjoyed Loki in Thor I did think the emotional balance of his character arc was mishandled. The story spent a lot of time on Loki's fairly legitimate reasons to be pissed, but glossed over that moral event horizon where he, you know, attempted genocide. In Avengers, Loki is charismatic, sometimes even sympathetic, but you never forget that he's a villain, either. Every time he does or says something that gives you hope for redemption, he turns around and ups the ante on evil. (I could've done without Thor's continual insistence that Loki is evil because he's mentally unbalanced, though. I mean, not that it was out of character for him, but Whedon does have a history of reinforcing the "crazy = dangerous and/or evil" trope and it's irritating.)
Meanwhile, Black Widow! Was freaking awesome. I was worried as her first scene came up that we'd be subjected to two hours of "The Girl" syndrome paired with Whedon's fondness for beautiful assassin-waifs -- it says something about how well Johanssen and Whedon handled the character that I entirely forgot my concerns two minutes later, and didn't even think about the issue again until after the film ended. She's tough, and holds her own on the team, but she's not a stereotypical Badass Dame who's unafraid of anything except her own psyche. On the contrary, despite being the most restrained character in the film, she seems much more in touch with her emotions than most of the others -- she just chooses not to express them overtly. And, like Loki, the moments she does appear to express them are never as straightforward as they appear, which might be why her big scene with Loki is one of the best in the film.
This is how to handle a heroine in a dude-heavy cast, people. Heck, this is how you handle a heroine in an ensemble cast, period. More than the Cap/Thor/Iron Man sequels, I'm now really looking forward to a Black Widow flick. Apparently
it's in Marvel's plans for the future, but we might have to wait for a while. Shucks.
Last but not least, the mid-credits teaser scene. Chitauri flunky tells a shadowed figure that to attack Earth now would be to "court death," and then the figure turns its head and we see it's ... Thanos, wearing the biggest smirk. Oops, should've seen that one coming.
I'd say I was possibly the only person in the theater who even recognized the character, but a pretty high nerd contingent came out of the woodwork, judging by demographics, people's t-shirts, and so on - so who knows. In any case, I've never particularly cared for Thanos, but now I'm actually excited for the sequel! (Especially if more ladies join the team, seriously. I'm rooting for Wasp or Ms. Marvel, personally.)