I just got back from seeing this. My first reaction was WOW! That was a great movie. I realize that I'm overly positive about almost everything, and I tried to look at this with a negative angle. There were a few subtle things that I didn't like, but they were so small that nothing is popping into my head right now. The new Spider-Man is great. He really plays the character well. And the whole "origin" story lasted all of 5 minutes. Marvel could easily do the same thing with the Fantastic Four, should they ever acquire the rites again, or work a deal with Fox for those characters.
Anyway, the movie had very clear motivation for all of the characters, except a few. I understand why everyone on Iron Man's side joined the fight the way they did, but they could have been clearer about Captain America's side. Specifically Hawkeye. Cap called him, so he's there. But what is the reasoning behind supporting Cap instead of IM? Same with Falcon, really. I mean, he's friends with Steve, but why did he decide to go that direction? Was he just being a Steve follower? I wish there was a little clarification to that. Actually, Ant Man as well, but I guess you could take the allure of helping some Avengers, but then again, why did he fight other Avengers? Oh well, it's a smallish complaint.
So the overall feel of the movie was great. It definitely felt "epic". I've read that it's the longest Marvel movie, so I'll accept that. It didn't feel long, though. There weren't many dull moments. The humor was good. Spider-Man talking non-stop during the fight scenes was awesome. It felt like Deadpool in that regard, except he didn't break the 4th wall. Black Panther was a nice new addition as well. He was a badass. If you're a fan of Marvel movies, you'll love this. If you're half and half about Marvel Movies, you'll love this. Even though this was only my first time seeing the film, I feel comfortable saying it's in my top 3-5. Ant Man, Iron Man, Cap 2, Cap 3, Avengers 1. Those are my current favorites. Guardians takes a 6th spot. And I'm not certain the order of my top 5, except that Iron Man and Avengers are towards the bottom of that list, but that's only after multiple viewings. Cap 2 & 3 are home runs. Ant Man was also a very fun movie (He's the person with "The Flash"s mentality in the Marvel Universe). Actually, I think that sums up the top 6. Cap 2, Cap 3, Ant Man, Avengers, Iron Man, Guardians of the Galaxy.
Stop reading this and go watch the movie.