re: Avenger: AoU Reviews (**MAJOR SPOILERS**)

I got the sense while watching the movie that Loki's scepter had kind of a One Ring aspect to it, in that it would try to get back to it's master. It makes sense, if Thanos originally gave an Infinity Stone to Loki, to have a back up plan for getting it back. Thus the "AI" inside Loki's scepter. Ultron was a perversion of that AI, so it knew about the mind stone (source of it's power) and was probably influenced, if perhaps not "consciously", by it's original programming. When the Vision came into being and Ultron destroyed, Thanos' backup plan to have the Mind Stone returned to him had failed, which is why he's going to take matters into his own hands.

But these are all underlying threads that connect the entire narrative that will culminate in Infinity War. They don't need to be explained in AoU, because Ultron and the Avenger's struggles are the key plots in this movie. I'm sure Thanos will monologue at some point, pointing out all the steps that led us to that point.

ETA: I enjoyed the hell out of this movie too. I would personally probably rank it above Avengers I, just a bit below GotG and Winter Soldier.