Kurt Russell is a charisma actor, fair and simple. But I kind of failed to understand the "purpose" he had for planting 'seeds' in other planets to destroy other life and remake those planets. Having children was just to increase his own power? Then why not direct invasion? That much I didn't get. I did laugh when Peter and Ego basically played a game of "catch" on Ego's Planet.
The Sovereign had a Ender's Game feel to them, except their repeated attempts to use drones to overtake the Guardians were kind of a nuisance at the end instead of a realized threat. Fortunately, Ego was a much more potent antagonist and I hope the Sovereign have a stronger presence in the next movie.
Rocket is at once the joke of the cast ("Trash Panda" has me giving a spit take) and at the same time, a badass. ("Oh shit, I'm using my wrong eye again, aren't I? I'm sorry, that was meant to be behind your back... [to Drax] Hey, you want to buy some batteries?") Yondu was given a great sendoff. I appreciated how they handled him where Rocket and Yondu figured out they are pretty much one and the same, and Peter/Rocket's bickering was similar to Peter defying Yondu in the first movie.
Baby Groot was cute, but it basically meant that the team of five was now four in essence. His presence was reduced a bit, and fairly so as Groot was a bit of a deus ex machina in the first movie protecting the team from the Infinity Stone's effects by sacrificing his body. So I didn't mind it as much remembering that.
Drax was the scene stealer out of the original cast. His naivete and bluntness came to the fore and that was welcome in this movie. You don't expect the deadliest brute on the team to be the comic relief unless they're inept, but he pulls it off and remains formidable. Batista was a great choice. (Runner up for the Scene Stealer trophy was Kraglin, Yondu's second in command played by Sean Gunn, James's little brother. "Yeah... I was talking about like a pretty necklace, or a nice hat, you know. Something to make the other girls go 'ooh, that's nice.'")
Gamora has some reconciliation with Nebula which is welcome, but as she's spending most of her time being the second in command, they're still playing the 'no time for love, Dr. Jones' card with her. She shows some signs of letting her guard down by the end, but if you're expecting her to stop withholding affection before the 3rd installment, don't hold your breath.
Finally, the audience advocate himself, Peter Quill. The main hook of the plot is why Peter's father was a mystery and how Peter's life was orchestrated from the start. As any hero does, he works past the villainous designs of Ego, overcomes his influence, and returns to space a little different than before. So in that instance, GOTG and GOTG Vol. 2 have that in common. But with his father's past reconciled, unless they intend to go further with his Mom's background past being a Missouri girl who fell for Starman, his past isn't likely to be as big of a part of a third installment, which will be an obvious comparison to separate the movies apart. All in all, the second go around wasn't terribly flawed.