Assorted thoughts!
Spoiler
The opening sequence almost put me off, with the very earliest action scenes as they ride in looking extremely fake.
Why did Ultron need to build that first scrap body rather than just controlling one of the others?
Ulysses Klaw was made to seem like a big deal, but then he just disappeared after that one part of the film.
Barton has a wife and kids? Is that something he's had in the comics? I've never heard about it if so.
I'm not sure if I liked the way Ultron talks. He was very casual, very human.
Deus ex Helicarrier. Does this mean Fury's no longer in hiding? Why was he hiding for this long, if he could pull together this kind of stuff anyway?
I was surprised they killed Pietro off in his first film.
The Vision saving Wanda could point at them setting up their relationship from the comics.
The Vision and Scarlet Witch are a bit weird and powerful for these films. The MCU is edging up toward the point where it stops being as accessible to non fans.
The Avengers, as of the end of this film, are: Captain America, Black Widow, War Machine, Falcon, Scarlet Witch, The Vision, and probably Hawkeye. These are the people in play for Civil War (well, we don't know about Ant-Man or Spider-Man yet), with Stark likely turning to politics in his retirement from heroing.
Spoiler
2) House of M. I say set up Scarlet Witch/Vision, kill The Vision at the end of Infinity War, and have Wanda trigger the House of M event due to her grief. Use this event to fold the X-Men continuity into the Marvel Cinematic Universe (you could even handwave it to bring Pietro back to life).