It's about as good as it had any chance to be

Rating: 7/10 (7 May 2018)

If you consider yourself a fan of the Marvel universe, you can stop reading here and just go watch "Infinity War". Of course, your mileage out of it will vary depending on your investment with the MCU, so it should be stated that while I have seen all the other movies in the franchise save for "Doctor Strange" (just haven't gotten around to watching it yet) and even a couple of their TV series, I wouldn't consider myself a big fan. That is to say, I don't generally rewatch most of the films in the series, though I have enjoyed all of them, some more, some less.
I was not expecting to like this movie as much as I did. Bringing together all the characters from 18 different movies, most of which I have half forgotten since their respective release dates, in a two-and-a-half-hour superhero science fiction action epic that inevitably is going to act as a jumping-of-point for another couple of sequels and also has to throw in fan service for people who have been following this franchise for ten years much more obsessively than I did, that sounds like a movie that could make my brain hurt a lot. Thankfully, "Infinity War" is about as good as a movie like that could realistically be. If it were any better, I would seriously have to call it a masterpiece.
Especially in its first half, "Avengers 3" is incredibly entertaining. The various meet-ups of Marvel characters seems fairly fluent (though there are a few convenient coincidences that drive the characters together), and the superhero banter rarely gets in the way of the story. Thanos is a good villain, and the script goes a long way in making him out as an intimidating and interesting threat.
The Russo brothers have also staged their action scenes quite well: Though there are a few moments where the camera movements were too quick for me to make out what part of the carnage I was seeing, most of the fight scenes are a lot of fun to watch, thanks to great cinematography (when it was filmed in an appropriate tempo) and choreography. For the kind of movie it is, there is even some restraint in those scenes, as the final battle doesn't outstay its welcome and most of the action scenes feature a rather small amount of villains - though fans of gigantic battle scenes obviously need not worry, there's enough of that, too.
Emotionally, the film is - as advertised - much darker than the rest of the franchise, though Team Feige is too smart to turn their flagship movie into a depressing, joyless melodrama. As in their own movies, the Guardians of the Galaxy sometimes even ruin emotional scenes for me with some ill-placed punchlines. But there's still many moments in which even amidst all the effects-heavy destruction you can see how good the actors in this movie are.
There are a couple of missteps that the movie takes, most of them all but inevitable. Not all of the 30+ main characters of the story would have needed to be in the film, and occasionally their presences are a bit distracting, if only for the fact that I found myself thinking "What is --- doing right now?" when a scene doesn't give them much to do and instead focuses on the bigger players. Furthermore, as was hard to avoid, making the Avengers split up into several sub-groups on their own individual quests means dividing the main story into many subplots, and, not all of them are equally interesting. Particularly frustrating is the part of the film in which a number of action scenes happen simultaneously in different places, yet as if that wasn't enough they also had to throw in a slower scene that runs concurrently (and would have fit much better into an earlier section of the film).
This film is far from perfect, but the fact that I enjoyed it at all is a minor miracle to me. If you've enjoyed (most of) the Marvel movies up to this point, it almost goes without saying that "Avengers: Infinity War" is a must-watch. I would not go as far with my praise as others have, but I did have a great time watching it.