I'm really mixed about this one. Not mixed on whether or not I liked it or not (I did, overall) but how much exactly I like it.
Definitely not a top tier Marvel film but not a bottom tier either. But even then I wouldn't call it "average" because there were actually a lot of awesome moments, but there were also some really boring or dumb ones. It did some things better than the first film, but some things worse.
Even as a fan of the MCU, one thing that has kind of erked me lately is how the shared universe concept, while allowing for some really fun storylines and ideas we've never had before in film series, at times things can start to feel very "TV-ish". And by that I mean, introducing a character or plot point and not to have it touched upon again for a while. Age of Ultron almost feels like a fuller middle chapter at times because of this, I feel. Each film is at the mercy of the previous one or the next one, which creates a great challenge for the filmmakers in creating one solid, tied up film. It's not necessarily a bad thing, it's just that certain things don't necessarily add anything to the film's.
But, I liked it overall. All the core characters were there doing what they do best with excellent chemistry and charisma. ScarJo had some really great scenes and might be the stand out of the film for me thanks to her scene with Banner at the farm. Really fantastic acting on her part. I liked Quicksilver and loved Scarlet Witch. ATJ was actually quite good here! (Where was that enthusiam in Godzilla, man?). Olsen is as awesome as she is beautiful, I really hope she gets a chance to shine in Civil War. Ultron and Vision were alright. Vision was fun for a minute then kind of became Thor 2.0 so maybe in the next movie his character will be more unique. Ultron had about the same motive and logic for his master plan as a Transformers villain did, but at least he had some fucking personality. Still a far cry from Hiddleston's Loki, but solid enough.
I thought the last shot of the film with Cap starting with "Avengers!", takes a breath to finish the phrase only to be cut off by the credits was really funny.
Like I said, I'm still really mixed. Can't tell if it's C+ or B- range, maybe another viewing will help me decide how much I liked it.