Chris Pratt was brilliant. Love all his little nuances and how ungraceful he was during the big battles. Gave a lot more realism to the character. Groot was the star of most the battle scenes though in a Hulk-in-Avengers kinda way. But obviously Rocket was the star of all the dialogue. The whole "12% of a plan" scene was just hilarious. The film was very self aware, without going too far into parody territory. The scene of them dramatically walking towards the camera in a line while they adjust their pants, yawn, pick at their ears etc is a fine example of that. Ronan was a legit intimidating enemy and they showed just enough of Thanos to build him up, without ever delving too far into him to take away from when he eventually shows up full time in Avengers 3.
Just on the whole a really enjoyable film and I now love the characters, having not known much about them prior to this.