One minor, silly thing that didn't work for me: [Brief very minor spoiler for a small part of the ending.] How could a sloth drive a speeding car? As slow as they react? I can't see them driving at all, period. (I know that was a joke, but still, it just didn't make sense.)
Civil War: I shouldn't be surprised I liked this movie as much as I did -- Avengers movies always work for me.
Putting everything behind a cut, since I'm not sure what's a spoiler and what isn't.[Spoilers.]
I was confused about a number of characters, they must have either been introduced in other movies or comics or something. The Vision? I had never even heard of him before. Ant Man? I know he has/had a movie coming out, but I was at a loss for anything more than that. I heard the name Black Panther before, and knew of him from the Avengers cartoon. I think we were supposed to recognize some of the more minor characters too, but I kept saying "Who was that?".
I hadn't expected Spider-Man to work for me, but he did. I liked him quite a bit. Including how young he was.
Speaking of ages, wow. Robert Downey Jr looked really old in this. I was having a hard time buying him in the Iron Man suit anymore.
I swear, I read a bunch of fanfics that had a number of pieces of the movie plot in them. I wonder if they came from the comics, or if the authors just guessed well? Like Bucky killing Tony's parents.
Speaking of Bucky, he was the best thing in the movie. He needs his own!
The fight scenes were great. I expected the Hulk to show up at some point though. I don't like that Wanda character much.
I was pleased that this movie addressed an issue I have with many superhero movies: All the damage done to the area and innocent people while they're fighting.
I'm probably forgetting to mention some things, but the movie ran longer than I expected, and now I'm late logging.