Just got back from it. I actually liked it a lot but it was not a perfect film by any stretch, not the strongest MCU film, and I have a headache now from watching it, I think. I will put any revelations of actual plot events in spoilers, but talk about general stuff openly.
I generally agree with the social media commentary about it which can be generally positive but also can refer to the film's "noise." I'm just not really sure how they could have done it DIFFERENTLY, considering everything they wanted to pack into that run-time. Also, while it is a single movie and people want to describe it based on that, the reality is that it is not just one film but the culmination of like 20 films -- a lot of groundwork was already laid for this film, and Infinity War basically assumes you have seen the other films so you're aware of the characters, their relationships with each other, the severity of what Thanos is doing, etc. It doesn't "breathe" as a single isolated film because it has assumed you've already done a lot of natural breathing in the other films, and this is a deep drive where you're just holding your breath.
One criticism I have is that it starts out BOOM, hitting the ground running, rather than giving time to get anchored into it. There's heavy stuff happening in the first ten minutes. It doesn't start like any other MCU movie I can recall. The whole movie has a feeling of being on edge, it's relentless. And there are a LOT of action sequences. If there are talking sequences, they are usually comic relief banter or something similar meant to just keep the film from getting too weighed down in the severity of what Thanos is trying to accomplish. But there are some dramatic moments / personally heavy scenes For example, I really like the interplay between Spiderman and Iron Man, but this was set up in the Spiderman: Homecoming film, where we see Iron Man (the perpetual playboy) suddenly trying to be an inexperienced dad / role model for a precocious teenager -- there are some moments in this film that are pretty meaningful and intense because they lean into our past knowledge of Stark and Parker.
I'm impressed they found a way to split 20-25 superheroes into various subplots, making use of everyone decently, and making it make some amount of sense. I've seen films that have abysmally failed in this regard. We've also seen how the ball was dropped by Justice League, which barely set up any of the film in the prior DC universe outings and was just kind of a mess. I think this film ended up being dark due to the severity of what was going on, while still feeling much lighter than Zack Synder's DC outings (which are just broody if not dismal).
They managed to make Thanos somewhat sympathetic, although it was overdone in a few spots and I wish they had had a lighter touch. Josh Brolin (who I was so sick of hearing about in film after film, I groaned when he was cast here) was actually quite excellent; I was wrong in my initial impression. One thing I really liked was more intuited subtext about Gamora and Nebula. We have their discussions of their relationship to each other and Thanos in the GotG films, but here what I really picked up on was: (1) Thanos really does see Gamora as his "favored" daughter and possesses actual feelings towards her in that respect, and (2) I don't think he really cares for Nebula much. Or she's just another patsy. Which is the irony... she views Thanos as a hated FATHER, whereas I really think he just never really viewed her as family in the same way. So when he replaced parts of her body with machine parts (referred to in other films), she took it as something very personal; I think he was just actually being capricious or indifferent, but never really viewed her as "daughter" per se... or more like she was a failed experiment, she just didn't have what it took like Gamora did. It's one of the more successful "deeper" parts of this film, which is lacking mostly in those kinds of moments.
But it's just all so damned much. Like, I don't how to have changed it, but I'm exhausted after watching it -- it's like being cranked up to 10 for 2.5 hours, without a lot of natural ebb and flow.
At least the fights in the film feel like they have consequences. There always felt like there was a lot at stake... and that anyone could die at any moment, no tricks. And the last 20 minutes of the film were just as ballsy as hell. Justice League was pretty lame in comparison, they didn't have the balls to really go where the material could have led. the MCU did not disappoint in that regard. Yes, we know there is a sequel in a year that will be a story following this one that will probably do something to course-correct, but fucking hell man, bravo on just really having guts to take things there and then drop it for a year.
So I'm kinda on the same response as merced. I would probably give in a 7.5/10 or possibly an 8, although YMMV depending on your attitude towards MCU in general and whether you like the kind of things this film/MCU dishes up. I'm just not sure what they could have done to improve it, due to the Infinity Stone storyline. It also worked better than it would have because they have made so many films setting this up.
My favorite MCU film is still The Winter Soldier.