Although I agree with most of the rest of this post, I was amused at this comment. While we were waiting for the midcredits scene, the people behind me were commenting on how 9/11y that scene was. And then someone pointed out that Man of Steel knocked down even more buildings, with people still in them, and didn’t bother to show any of the ground-level aftereffects. This was a building they specifically called out as completely empty, yet they still showed that the people around it were kind of traumatized. I think Whedon was using more than Sokovia to refute the dark grim high-collateral-damage superhero movie thing.
Otherwise, I was also amused that they basically turned the Scarlet Witch into Jean Gray - Maria Hill rattled off “[something] telepathy, [something] telekinesis, [other thing] - basically she’s just weird”. Jean Gray’s random powers seem to be a bit more explainable than hex bolts + chaos magic, I guess. Same reason that the Vision didn’t have his density control powers.
My only real complaints with the movie were two: Falcon was specifically in pararescue; if Fury was showing up for a rescue operation (as he seemed to know would be needed), why not bring the rescue guy along? (for that matter, did they really have a helicarrier mothballed within a day’s travel to Sokovia?)
The other problem was that I think they made Banner’s characterization inconsistent. He first allows himself to be argued by Tony into making Ultron. Given what we know of his concerns about the dangers of power, he should not have then allowed himself to be argued into creating the Vision, too. That would have been better served, I think, by having him originally argue that they should put the Jarvis AI into the Iron Legion, so when Tony’s idea turns out to be pants he could then conceed that Bruce had been right. (also: Thor shows up and jumpstarts the Vision without telling his teammates for increased dramatic tension… but that’s the same thing they’d been on Tony’s case about.)
However, this was an astonishing film even with quibbles, just because of how ambitious it was: It was a summer blockbuster, that included quite a bit of character development. It introduced a bunch of new characters, to deal with upcoming contract expirations. And still managed to have all the many main characters meaningfully contribute. It set up the Infinity War storyline. It set up Captain America: Civil War. It set up Thor: Ragnarok.
The Superman v Batman: Dawn of Justice trailer was one of the (many, many) previews we saw. I have no confidence that movie will be even a fraction as successful as this one, at accomplishing even half the tasks that the producers obviously set for Age of Ultron.