I just got home from seeing this, and here's a quick non-spoiler review.
I've heard a few people mention that this movie isn't top tier. It was fucking great. I would say better than the 1st, but maybe it's because I had such a good time at the theater.
Every character had "holy shit, this is awesome!" type action moments. The exception being Groot, who danced. He's too small to have much action, though. They pulled it off in Ant Man, but in this movie, everything was large except him, so he was primarily there for comedic relief. The story was well done. The characters had incredible chemistry. I legit "felt" for them at various points throughout the film. The character, Ego, was very well done. His name matched his attitude, which helped. It also explained more of Star Lord's back story. Also very beneficial. As time passes, there may be some things that I'll likely stop remembering through rose colored glasses, but as of right now, I'm very happy and impressed. I have absolutely no complaints about this movie. Also, there's like 12 "after credits" scenes. All of them related to GotG, except the very last one. Still not a complaint. I loved the sound track, with the exception of the two songs that only played during the credits. And even that is because I didn't previously know either of them. The rest of the music was perfect for each scene. I'm very happy with this movie. It was long, but not even close to slow at any step. I remember the first one had 1-2 moments where I looked at my watch, realizing that it was long, but this didn't give me that feeling at all. As of now, the rest of this year has me looking forward to Spider-Man & Thor. Even the Inhumans IMAX release for September 1st. Then eventually Guardians 3. I wasn't expecting either of the a-list actors that showed up. They might have been spoiled in a trailer or imdb, but I haven't been keeping up since the very first trailer dropped a few months ago.
Lastly, the main boss battle sequences were reminiscent of Avengers 2 and the Ultron fights. This isn't a bad thing, but I think they really perfected the same fight style in this movie. A+, can't wait to see it again.