I'm way behind the curve on getting to see this one, but it was really good!
Baby Groot was flawless (and the two scenes with him being in distress were surprisingly distressing.) He's treated like a literal baby, so when you see him being threatened or scared and having beer poured on his head until he's that dejected little seedling that doesn't even notice Rocket until Rocket speaks, it really hits. And the "buried alive" scene where he was crying like an actual human baby was crushing. Having him grow up may be one of the biggest mistakes in the coming movie(s).
I think Kurt Russell was spot-on as the embodiment of Ego, as was Quill's response when he found out what happened to his mother. Christ Pratt's really good at toeing the line between the Guardian version of his character and the one that's still the little boy from Earth.
The Taser-face thing went on for far too long, and it was never funny to begin with.
The interactions between Nebula and Gamora have never felt right to me, and this movie didn't really do anything to improve them. Likewise, half of Drax's scenes with Mantis weren't quite on point, but the ones that worked, *really* worked. Little details like him keeping her above his head as he sank into the ground that really show off his character.
I also liked the video-game atmosphere created for the Sovereigns' ships. Everyone gathered around the last guy standing and cheering him on had a real arcade feel to it.
All minor things. My only real complaint would be with the handling of Yondu.
1 -- GIVE ME and Yondu and Rocket "buddies on the road" movie RIGHT NOW. Those two were perfect together.
2 -- the Yaka Arrow. The way they portray it in the movie, Yondu should be the single most feared being in existence, including Thanos, The Collector, Red Skull, Loki, dark elves, Ultron, Hydra, Hulk, and Hela, even if all of those guys teamed up.
3 -- Given the ending, there should have been more flashback scenes with young-Quill and Yondu, similar to the one he recalled of Yondu teaching him how to shoot. Specifically, there should have been a scene of Yondu teaching him how to use the arrow. Because at the end, it would have been so much more satisfying to see Quill fly "his Daddy's" arrow to the center of Ego's planet and stab his "father's" brain, than it was to see Ego explode.
4 -- I get why they went the route they did with Yondu's end, but it was completely unnecessary. That thing that Quill wears behind his ear, the one that controls his helmet, was enough to keep Gamora alive in space in the first movie. It was enough to Quill alive until he gave it up, even without the thermal shielding. It would have been enough to save him or Yondu, either one, at the end.
(Oh, and one more thing -- I HATED the scene with the ravagers after the mutiny.)