Just saw it a third time. IMAX this time.
Some thoughts ...
Thor is a bad-ass, finally. He showed glimpses of this bad-add-ness in Ragnorak ("Tell me who's ass I have to kick!"), but here he is just on top of his game. He demonstrates emotional range with the deaths of both Heimdall and Loki, to his energetic arrival in Wakanda and his final battle with Thanos. This was the Thor character that I think everyone has always wanted.
Cap had a nice entrance as well when he caught that spear and came out of the shadow. But overall I thought Cap was a bit of an after-thought in this movie. At least until he caught the Infinity gauntlet with both his hands and took that blow from Thanos' right fist. I think the lack of his vibranium shield made me think he's an after-thought. I get why he didn't have his shield, but I guess it'd be like seeing a movie featuring Batman and there's no traditional bat-arang or batmobile or what-have-you.
The Guardians ... lots of comedy there. Drax being Drax. Quill deepening his voice. Teenage back-talking Groot. But there was a lot of really good and serious moments here as well, Gamora being prime among them. Being Thanos' adopted daughter, one had to know she would factor in heavily in this movie. I got a good sense of the level of anger she felt toward Thanos. She thought she had killed him at Knowhere, but of course the reality stone was in play; that sobbing while her "dad" lay there bleeding out, before the work of the reality stone was revealed, got me all knotted up (my daughter will tell you she has me wrapped around her little finger and can whip out the tears to get just about anything she wants (she's wrong, but she'll say it's so)). Then, I knew the moment that Red Skull said a "soul for a soul" that she was going to die, yet that was still one of the movie's top emotional moments.
In a movie with this many characters, I was glad that everyone got some meaningful screen time.
Music - I loved the Rubberband Man song inclusion when we first see the Guardians, and I am also happy that they brought back Alan Silvestri to do the score (he did both The First Avenger and The Avengers, arguably the best musical scores in the entire MCU).
Finally, Thanos. Wow. They've been teasing him ever since the first end-credit scene in the first Avengers, and did they ever deliver. I felt like he commanded every scene he was in. It was much like way back in 1989 when Jack Nicholson's Joker was on screen - you just knew he was this bad-ass villain who you absolutely could not take your eyes off of. Same thing with Thanos. I know some have questioned his motivations, but really, how do you think they pull off something like wanting to impress "death"? Not being real familiar with his entire story, what does that mean about "death"? Is that some character that we've never seen, or I think I recall that Hela in Ragnorak was referred to as "death", surely not her given that she could not even defeat Thor or that fiery thing. Thanos is a villain, but he's a baddie with an emotional core that seems real enough, as seen with his interactions with Gamora.