Not a review, per se, but just some collected thoughts...
MAJOR SPOILERS BELOW—BE WARNED!
1. Loved it. It started like a Bond film with an intense action sequence, expertly shot in a similar fashion to the Battle of New York in the first film, with the focus flowing seamlessly from one character to the next, then calmed down as we saw the threat of Ultron building. Then it was off to the races again, only to be followed by setback, then regrouping for the final battle...
2. ...which was focused on SAVING ALL THE PEOPLE.
3. They SAVED ALL THE PEOPLE.
4. ALL OF THEM.
5. Ok, where was I... oh, right.
6. The focus on the six main Avengers seemed much more even this time, with Black Widow and Hawkeye getting more attention (especially with the surprise revelation that Hawkeye has been married to Velma all this time—no womanizing cad this Clint Barton).
7. I wish Black Widow hadn't been made the captured Avenger that had to be rescued, but that role was played by Hawkeye in the last film, and the others are too powerful. But still.
8. The humor was fantastic—I tried to remember all of my favorite lines but last track twenty minutes into the film. And they weren't all one-off gags: the running joke about Cap's early comment about "language" was fantastic. Even the scene from the preview with the Avengers trying to lift Mjolnir set up Vision's validation in the face of his new friends.
9. The new characters were integrated extremely well. The early antipathy of Quicksilver and the Scarlet Witch Pietro and Wanda towards Stark and the Avengers was easily motivated and then dispelled gradually. I was surprised not to see Pietro healing at the end of the film; Wanda was the more longstanding Avenger of the two in the comics, but nonetheless I liked their relationship in the film. And the Vision, wow...
10. The Vision was simply magnificent. One advantage of attending the first showing of the film was the number of diehard fans in the audience, all of whom applauded when Vision rose from his "cocoon." (Not to mention the gasps the first time Wakanda was mentioned.) Paul Bettany played Vision with the quiet dignity he deserved, and I can't wait to see him again.
11. I was a bit put off by Ultron's sense of humor, which is a distinct departure from the comics, but it grew on me, and made excellent use of James Spader's voice talents. And visually, he looked amazing.
12. Similar to Guardians of the Galaxy, teamwork was the focus of this film. The Avengers never really disassembled (even after Wanda's mindgames), so there was no need to rally at the end. I'm talking about the subtle, small types of cooperation, such as the one-two fight moves that Cap and Thor had obviously worked out in practice, and the way Clint and Natasha had each other's back throughout the film.
13. The cameos... well, I won't spoil those. There was Stan Lee, of course, but other MCU players made welcome appearances as well.
14. While the mid-credits bonus scene wasn't spectacular, it was gratifying to see the names of all the heroes—Avengers old, new, and "see ya next time"—in the main credits preceding it.
15. Tony, Tony, Tony... when will you learn? (What am I talking about? See my new post at the And Philosophy blog.) Also nice to see the continuing ideological differences between Tony and Cap referenced but not stressed (there's time for that in Captain America: Civil War).
16. I can't stress this enough: the last quarter of the movie was as much about getting all the people off of the floating city as it was about defeating Ultron. That's what the Avengers risked their necks to do. That's what Fury and Hill brought the helicarrier back for. That's what Clint almost died for—and Pietro did. It's sad that this kind of heroism is notable in a superhero movie, but in a Zack Snyder world, it is.
17. And did anyone fear for reality a little bit when Wanda lost it after Pietro died? I half-expected to see little Tetris pieces flying around.
18. And finally... Natasha and Bruce. I like it because it felt organic, and the scene in which she shares some of her Red Room background with him justified it even more. And of course, Bruce's "I can't be with you, I'm a monster" speech was well appreciated by this Thing.
P.S. It's Natasha Romanova. It's not too late to correct a grievous wrong. Respect.
To sum up, Avengers: Age of Ultron took advantage of the fact that it started with a team already assembled to jump head-first into the action and then spared no time in bringing the main threat to the stage. It was extremely well paced, with excitement, humor, and pathos throughout, and terrific performances by everyone involved. If this is Joss Whedon's farewell to the MCU, he couldn't have done a better job—this was a love letter to the Avengers, Marvel Comics, and to Marvel Zombies everywhere.