I wish we got to see how Ultron inhabiting the Internet affected the world. Really disappointing that all the info about his net powers arrives through exposition.
I still don't get how exactly he was created. I get that the staff was involved, but why does the interface click for Stark and not for Hydra? They were obviously building robot bodies for AI to control, and Ultron himself utilizes them when he escapes the Avengers tower. So how much is Tony to blame? How much of Ultron was Hydra's work on the stone? How much is the stone itself? Is Ultron a manifestation of whatever intelligent code is within the stone (like a celestial AI)? His introduction is cool but his origin remains unclear.
I also never understood his desire to see the Avengers fail. Is it meant to be opposed to Tony's desire to see the Avengers succeed? Ultron really drives the point that his plan is about the world seeing the Avengers try to fight but lose, as if that would make them responsible for whatever destruction ensues. I didn't get it. Like, if Thanos was somehow communicating or influencing him through the stone I could imagine it (as it's been shown that merely being around the staff twists people's minds). But I can't figure how he would develop that motivation on his own.