Firstly, I must say that the movie does deliver when it comes to excitement and well choreographed action; unlike the recent "Spider-Man: Homecoming" and "Thor: Ragnarok," where the fighting went on and on and seemed boring and sloppy.
The humor is also slightly better than other Marvel films where comedy is "attempted." Also, the gags and one-liners were timed well and did not interfere with drama scenes, as they have before, taking the seriousness out if it.
And of course, the most anticipated element of the film was the rumored "shocking" finale. The end of the movie was indeed a surprise, which makes it exciting to look forward to the next installment. There are some superheroes that were either underused or did not appear at all, but I imagine that Marvel will work them in next time.
Most of the actors gave strong and not-too-hammy performances, and the plot actually made some sort of sense (aka they tried to explain it).
The only downsides were the completely unrealistic stunts (but of course we expect and enjoy those in a superhero movie), a few slightly cheesy lines, and a very brief moment of painfully bad CGI. And, I'm sorry, but I'm kinda tired of Stan Lee's inevitable cameos. It was funny the first 20 times, but now it's getting a little old. But that's just me.
So all in all, I was impressed with "Avengers: Infinity War," I will definitely see Part II, and that's really something coming from me!