I'm definitely going to wind up seeing this, because basically I enjoy all the Marvel films, even Thor 2. However, there are a couple of points that bother me.
1. Character overload. They've got all the Avengers, old and new, plus Spider-Man, Ant Man, Doctor Strange and Black Panther, plus the Guardians of the Galaxy, plus various supporting casts from the respective franchises. There are still characters who haven't been properly explored, because they made their debut when the MCU was already pretty crowded. I have no idea what Vision's powers are, for instance, and I have real difficulty giving a shit about the Winter Soldier.
2. A boring villain. I mean, yeah, Thanos is supposed to be this badass motherfucker, but all we've really seen of him is a guy who sits around and orders people about. There's nothing about him that makes me want to know more. And if he's competing with about 40 pre-existing characters for attention, I doubt that's going to change. IMO, they should have done something like they did with Loki, where he's an antagonist in another film, then he becomes a much bigger threat.