I thought Thor's intro was very cool, Iron Man's may not have been overly cool but Iron Man in the movies is more about Stark and he got a neat intro. Black Widow probably got the best intro, and the Banner intro was just more interesting in how Ruffalo played him. And then CA's intro, well, we pretty much saw it in his own movie but it was good as it -sort-of- showed us his recovery. But BW certainly got the best introduction.
(Save maybe Hulk's official introduction in the Helicarrier.)
I just got back from seeing it again (and will see it a third time this weekend in 3D) and, man it's still a very satisfying, fun and cool movie. Beyond nitpicks I really don't think I can find any flaws with it.
New nitpicks:
There were times when under Tony's Black Sabbath shirt (and granted he was wearing another shirt under that) you couldn't see the glow of his chest arc-reactor. Now, granted, one could argue it was obscured by the two shirts but then there were other times you could see it.)
The climax with Tony doesn't make much sense when scrutinized. He aims the nuke to go through the wormhole, in theory that's all he should need to do as the rocket's own engines will push the nuke through the wormhole and into the alien ships. There was no need for him to actually go through the wormhole and I'm not sure how he "fell back into it" (no gravity in space and all) but I suppose Earth's gravity could have been working through the wormhole and still had a latch on him because I guess he'd technically need to reach escape velocity even if Earth's footprint through the hole was tiny. But the scene plays well into Tony's "arc" in this movie with him sacrificing himself when the time came as alluded to when he was fighting with CA.
Things I noticed:
The weapon Coulson uses on Loki made the same noise the Destroyer did when it fired. (I'm guessing the weapon's technology was based on salvaging its remains after the events of Thor.)
I think Joss Whedon's "foot fetish" came into play a bit here with Paltrow padding around the new Stark Tower's floor in bare feet as well as Natasha padding around in stocking feet after her "interrogation" with the Russians.
I convinced Fury's "my boat" line was a Firefly nod. While technically calling the Helicarrier that is valid it's just an odd term for such a ship.
Anyone who doesn't think a Black Widow movie will work needs to watch this again and pay attention to her scenes particularly the "interrogation" scene with the Russians, her playing Loki, her talk with Hawkeye in the infirmary and then them talking during the big battle at the end. (BW says the fight reminds her of [some other one] and Hawkeye says back, "You remember [that place] very differently than I do."
Really, I think ScarJo did a great job in all of her scenes (again, superficialness aside).
For an afternoon showing on a weekday the theater was pretty crowded and the audience still laughed at all of the "right times" and with the beats of the movie. As with the other night Hulk pounding Loki got the biggest laugh masking his "Puny god!" line, as did Hulk punching Thor and then Hulk roaring to rouse Tony.
Really, I think this movie is just tons and tons of fun.