Finally caught up with it and saw it. It's so close to being great, but as Trey said, the story is overly cluttered, and I really think they dropped the ball with their ending. The whole appeal of this story is that they're not superheros, they're just ordinary folks coming together to save the day, and then they pull a bullshit
SPOILER
Show oh, you can hold the stone because your father is actually some ancient galactic super-race or some shit. I'm so sick to death of this pre-destination bullshit, why can't he just be an average kid?
I would say the first half is fantastic, and the 2nd half needs to lose about 25 minutes of plot and repetitive action and replace it with more of the characters just hanging out together. You know, having a massive end-movie dogfight battle is a lot more impactful if you didn't just do a big mid-movie dogfight battle 30 minutes ago.
All that being said, it's easily my favorite of the marvel movies, the closest to something that genuinely feels like it has a personality to it instead of their usual generic machine-like productions. It's also the first of their movies I've seen where I think the cinematography is great and that's got genuinely impressive FX work throughout. I've complained in the past about how flat and TV-like a lot of their movies look, but that's definitely not the case here. Great designs, integration of practical and CG, and creature effects (I thought Rocket was great for the record).