Joss really is a master, isn't he? Such a great job. I'm sure he feels good about going out having done what many thought was impossible in delivering the Avengers to the big screen.
Cons:
Very few, but one thing that might sound weird: I saw it on a huge screen, and I sorta wish I had seen it on a smaller screen, and look forward to seeing it on my TV. There is just SO MUCH going on in every shot, especially during the fights, that it seemed to run together at time. That's not much of a con, I realize.
The Infinity Stones talk was a bit "on the nose," but I get why they did it the way they did. Especially with time constraints, you just have to put it out there as plainly as possible.
Agree with others that I'd have liked to have seen some of the AoS crew on the bridge of the Helicarrier. No lines or anything, and no Coulson, but if Fury had to put together a skeleton crew to operate the carrier, who is more available than Coulson's team? Would have been a nice nod if May was in the shot giving orders in the background, or whatever. Just a nice nod to fans of the show.
Somehow they never mentioned the twins' origin in a way that referenced Inhumans or the diviner or the terrigen mists. I'm just more surprised than anything.
Pros
Wow. So many. Ultron was great. I've read people saying he was too snarky and emotive, but I loved it. I didn't want to see another mechanical, emotionaless automoton. They took it totally the other way and hit it out of the park.
Such great humor. Such great action. Such great everything.
Remember when RDJ was a washed-up has-been and Marvel was crazy for picking him up? And he got second billing to TERRENCE HOWARD?!?! lolz
Speaking of, I loved War Machine getting the screen time. It was all hands on deck, and we got all hands.
Thought Vision wielding the hammer was one of the best set-ups and deliveries I've ever seen.
Hawkeye absolutely stole the show. He was basically a non-character in the last one, but Joss made it up to him in a huge way.
Other thoughts
I'm feeling pretty secure in what was once just a wild theory. At some point there is going to have to be a "was for Cap's shield" type storyline, obviously. Bucky and Falcon will both claim the title. I'm telling you that Natasha will be in the mix for that as well. Her role as Cap's de facto sidekick is a big part of it, but she's also handled the shield very pointedly a couple of times. I just don't think it's a coincidence.
Because Cap and Stark parted on good terms, I'm now fairly certain that the big Civil War trigger will take place during Ant Man. You'll have a non-Avenger rogue superhero (Ant Man) that is going to royally screw up and innocent people will be killed. That will initiate the ideological conflict.
