There's a reason why this movie has Hulk Smashed box office records. Quite simply, it is awesome.
Wikipedia covers the essentials here.
At one point in the movie, Loki decides to announce his plans for world domination to a crowd of Germans. He forces them to bow at his feet and then, in a grand speech typical of this genre's villains, he declares that freedom is not the natural state of mankind -- that we are happiest when we are being ruled. The aforementioned crowd listens in silence, terrified of the demigod who holds forth before them --
-- and then an elderly gentleman stands up. He stands up and declares that the world has seen - and defeated - men like Loki before. Loki scoffs: "You have never seen a man like me." Quoth the old man: "There are always men like you." (This is a paraphrase from my memory, of course, but I think you get the gist.)
This is a movie about superheroes - men and women who possess remarkable technology (i.e., Iron Man), super strength, or inerrant aim (i.e., Hawkeye). And yet, in the scene described above, Joss Whedon takes a moment to feature an entirely ordinary hero -- someone who has no hope in hell of defeating Loki but is still willing to risk a kind of martyrdom to stand up for what is good.
Similarly, when Loki escapes from his cage on Fury's flying aircraft carrier, the Avengers essentially fall apart -- but Agent Coulson, the regular guy who spends much of the film in total fanboy mode over Captain America? Coulson manages, for a moment, to best Loki with a very large gun and eventually dies for his trouble. Subsequently, it is Coulson's sacrifice and his belief in the Avengers that inspires Stark in particular to put aside his ginormous ego and accept his place as a member of a team.
Personally, I wish Joss had hit the pro-freedom notes a little harder -- and I also believe the movie is somewhat unfair to Fury, who honestly had the best interests of the planet in mind when he decided to use the Tesseract in his weapons development project. But because Joss does such a marvelous job exploring the concept of heroism and what it truly entails - because he emphasizes, repeatedly, that heroism arises the moment you empty yourself and submit to a noble purpose and that your superpowers really have nothing to do with it - I'm largely willing to put my complaints aside.
Many of the reviews I've seen for this movie emphasize - and not altogether incorrectly - that it is pure fun -- an action-packed "spectacle" that cleaves to the grand tradition of summer blockbusters. But I believe Joss's script goes deeper than that. Yes -- the superhero formula has been left intact. Yes -- there are plenty of explosions. And yes -- because this is Joss, there is also plenty of humor. But if that were all The Avengers offered, I would've awarded the movie a solid B. No -- this movie makes it into feature territory primarily on the strength of its characterization (though, as I said above, the thematic elements help as well). I wouldn't say Joss' talent is applied evenly throughout the ensemble, but even the Black Widow and Hawkeye - the least utilized of the six Avengers - get their chance to display their fundamental humanity.
Of course, in my opinion, the character arc that truly stands out is Tony Stark's. And I'm not just saying this because I have a thing for Iron Man and Robert Downey, Jr. Objectively, Stark is the character who grows the most throughout the film. At the start, he is - well - himself. He announces that he doesn't "play well with others," pokes Bruce Banner with sharp implements because the concept of the Hulk amuses him, and basically drives Captain America insane with his refusal to take things seriously. Indeed, at one point, Stark's behavior prompts the Cap to proclaim self-righteously that Stark would never "make the sacrificial play" and leap onto a grenade for the others. But once things go pear-shaped on Fury's ship, Stark completely turns around. Though he's still lovably roguish in that way we've come to expect, he also willing to accept the Cap's leadership of the group. Most importantly, against all expectations, it is Stark who takes on the crazy-dangerous task of diverting the nuclear missile headed for New York during the final climactic battle. To be perfectly honest, Joss scared the crap out of me with that one; for a moment, I was afraid he was going to kill off Iron Man.
So yeah -- as I said at the start, this film is awesome, and not just because it features lots of things going boom. Go! Get thee to a theater and watch!
See the discussion above.
I wasn't that impressed with Chris Hemsworth's performance as Thor, but I loved Mark Ruffalo and Robert Downey, Jr.
Production Values: 8.5
Nothing screams "Feature worthy!" on this front, but the effects are satisfying.
Again, see the discussion above.