The spoiler free write up will (obviously) be a LOT smaller then the spoiler version, and it's more apparent for this movie, there is a LOT that happens in this movie. First of all, if you're still worried about Marvel's villains, don't. Thanos is an amazing villain, both in motive and strength. They establish that he is to be taken seriously right off the bat. The comedy in the movie is still there, at this point if this is a deal breaker for you, I'm not sure you'll really enjoy any of the Marvel movies as they are here to stay. I can however say that the comedy is controlled and has appropriate timing, much more appropriate then Ragnarok.
Also if you are going in expecting equal character moments for every character, then you will be disappointed, however I can say that would be too outlandish to do properly without it impacting the movies flow. What I can say is that the characters at this point have been fleshed out and seeing new interactions was very refreshing to see. The acting as usual was on par, and Josh Brolin absolutely KILLED it as Thanos. Thanos has become one of my favorite villains, I was afraid he was just going to be "kill everyone because I want to" but his motive made sense and he truly believed what he was doing was right.
The action scenes were very well done also as expected, seeing the new combos between characters was also really cool to see especially those who have read comic books before. The flow and cuts back and forth were really well done and didn't break it to the point where it gets annoying for the audience.
The finale would definitely annoy many viewers especially those who forget this part 1 of a 2 part series. But rest assured the cliffhanger leaves you begging for more. There are a ton of questions that will spark an insane amount of fan theories for the next year. Infinity War has been without a doubt my favorite Marvel movie to date.
For a more in depth explanation please check out my spoiler review.