Just go see it, if you're a fan of the genre...believe me, you'll love it.
They ALL show up - Captain America, Ant-Man, Spiderman, Hawkeye, Falcon, Black Widow, the Scarlet Witch, Don Cheadle (what's his character's name?), Iron Man, and Paul Bettany (be still my heart!)
Sadly, no Hulk.
There's a new character, Black Panther. Loved him and his philosophy.
The movie is 2-1/2 hours long, but it didn't feel long, in fact it went by very fast with all of the action.
Basically, the plot is that the "government" wants to control the Avengers and Captain America says "no." Each of the Avengers takes a side - action! There's lots of guilt over collateral damage, but surprisingly no blame for the bad guys who caused the problem in the first place. Where was that mentioned? Not even once. Seriously guys?