I'm a comic book fan, an Avengers fan. I laughed out loud a few times at this movie, would give it a "that was OK", but I'm not particularly an Avengers 2 fan.
Here's why: **WITH SPOILERS**
Avengers 2: Age of Ultron - http://www.imdb.com/title/tt2395427/combined
1 - Romance with Hulk & Black Widow - totally unnecessary, non-cannon material. Hulk character development was missed, Black Widow has self-hatred.
2 - Scarlet Witch & Quicksilver - not well utilized, arbitrary death (which is a Whedon hallmark, unfortunately). Witch seemed to have 3 lines. (I was elated that Quicksilver was Kick Ass -- but then he was unnecessarily killed, which was a crushing blow.)
3 - Hawkeye's secret family - 99% sure this isn't from comics, 100% sure it wasn't EVER necessary. The only reason I'd want this godawful segment, which I didn't, was to see Hawkeye croak. He's an awkward enough hero, but so easy to replace -- get the next schmuck a bow & neat arrows & no powers. Done. (Where's his dumb mask, btw?)
4 - Vision & Ultron - all the joy/villainy of these characters was bypassed. Ultron didn't make much sense, and radically departed from his comic self -- and why did he need to have animated metal lips AND an anatomically incorrect body? Make a metal dong, or make him cyborg smooth -- but you can't have both. Vision -- so much opportunity to have a Spock-like logical rational non-humanoid entity, so little exploration. Jarvis' humor was only good as a sidekick to Robert D Jr's over-the-top ness.
5 - Thor & hammer -- meh
6 - Captain America -- did he even get any opportunities in the film?
7 - Iron Man -- how could HE get upstaged?!??!
Final parting disappointments:
No after-credits scene (no schwarma w/new team??!), mid-credits scene wasn't really 'a scene'. Plot was a chaotic maelstrom. Wakanda / Vibranium piece was unnecessary. Endless Ultron drones = zero tension. Seemed like 5 long unnecessary fights, would have done better with a few meaningful encounters. Scrapping Pym was a mistake, he and Wasp are core to Avengers.
Nick Fury has what? I thought he was going underground somehow, not running around with a giant ... you-know-what.
Anyway, I probably could whine more, but I'm going to have to watch it a few more times to see if I missed some hidden gems and somehow wind up liking it more. For now, it was a C film -- damaged by too much money & talent, but desperately needing help with the writing / plot.