I went to see Avengers: Age of Ultron last Thursday, when it opened in Korea, with my son. Since it still hasn't opened everywhere (and I'm maybe just squeaking this in as a "blog brag" that I've seen it and you haven't), I'll keep this spoiler free.
First of all, for those searching Google for "Avengers Age of Ultron curse words" and finding this post, yes there is some bad language in the film. In fact, there's a running gag about it. But there's not a lot, and much less than in Marvel's Netflix Daredevil TV series.
Overall, I liked Avengers 2. They introduced the new characters well, brought in some old minor characters, and are setting up the transition from the original cast to the "next generation" of Avengers. Contracts for the stars only run for one more (two part) movie, from what I hear.
The movie has a darker tone than Avengers 1 or Guardians of the Galaxy. There are jokes and humor in the movie, but it's muted. Or maybe just not as funny this time around? Joss Whedon isn't infallible, after all. But the action is intense, the plot is character driven, and it's setting up the events to come in the next wave of MCU movies.
One thing that did surprise me (this is a tad spoilery so highlight the black bar to see it)
they didn't introduce any of the Phase Three characters, Ant Man, Black Panther, Dr. Strange, or Captain Marvel in this film. I didn't think they'd have time to work in a Spider-Man cameo, but since Ant Man is coming up in a month and part of the film takes place in Wakanda, I thought they might have an after credits scene at least introducing one or both, but they don't.
How would I rate this film? It's pretty good on its own. As far as compared to the other MCU films? Not at the top, but up there. It's not as fun as Guardians of the Galaxy, it doesn't have the rough, rock n roll feel of Iron Man 1, and it's not as much of a roller coaster ride as Avengers 1 or Captain America: Winter Soldier, but it's solid.
Hawkeye and Ultron really stand out as strong characters in this film, and I really like their take on the non-human intelligences of Ultron and Vision.
If you're an MCU fan, you're gonna go see this anyway regardless of what I write. But if you're on the fence, I'll ask you a question. Do you want to see a semi serious take on super heroes and the stress that having to "save the world" puts on them, with some awesome fight scenes and a lot of fun references that comic book geeks will get? Then go see it.
If not, then save your money for Mad Max Fury Road or Terminator Genesys or something else that strikes your fancy.