Saw it last night. Was very good, but IMO, not better than Avengers.
I thought Lee Pace did a great job with what he was given as Ronan, but they could've done much more with his character. Wish we would've gotten a little more about him, his motivations etc...I still don't know why he was so upset with the Xandarians...something about a peace treaty. Also would've liked to see him as more of a threat especially towards the end.
As mentioned, Groot and Rocket steal the show. Both look and sound fantastic. Bradley Coopers voice is unrecognizable in the best way, while Diesel's voice is as trademark and perfect as ever. Drax is funny and looks cool. Pratt as Quill does a good job on par with Hemsworth as Thor but not quite as good as Downey/Evans.
I thought Gamora was too soft. She needed to be a little harder and less sentimental. Probably my least favorite of the cast.
Overall, the pacing and action are good, characters are great, plot is ok. 10 more minutes to flesh out some character motivations, action sequences and story lines would've made this film much better.
I'd give it 8/10.