OK, here it goes...
No specific details yet, but here's my feelings...
I think they tried to ESB this movie. Split up the heroes so there's lots of cutting back and forth... but the group works best when its a group. The separate storylines seem... trite for the most part. There's some fun, and quite a few laughs, but ... it is no where as good as the first movie. There's no mission, no adventure for the Guardians to pursue as a team, and tragically, no real villain. The bad guys assigned to 'play the fools' are used at the expense of jokes.
There's also very little swindling and cheating, which was the best part of the first movie. And Star-Lord is so enamored with his new Pop that he isn't even the same character for half the movie. There's no 'dance-off bro' (which is good), but there's also not much Star-Lord there either. Just a lost little boy.
The entire movie feels like it has no direction -- meaning movement forward -- which you will realize within the first 10 minutes (as soon as they land in the forest). From there, the story just meanders along, dividing into several predictable subplots with characters having self-realization moments, and lots of jokes... the best of which you saw in the many trailers. Too many.
There's the standard 'big climax' -- which makes no sense really -- and is awkwardly complicated, and then quickly wrapped up with unrealistic solutions.
There is a 'big surprise' -- but anyone with two-cents will see it coming, or if they didn't, they will nod with the 'of course' once it happens.
There's some surprise cameos as well -- well, only a surprise if you haven't been keeping up with Marvel's current business model. Seriously, the casting choices of late seem driven by the 90's sensibilities in casting for the Burton/Schumacher Batman films.
So, as you can guess, I was really let down by this movie. Perhaps I expected too much (this was my most anticipated movie for summer). I would have liked more adventure to balance the silly humor and music. That's not to say it isn't fun. It's got a warm heart, and lots of jokes, and even more music... but this movie is pretty much the trailers and the goofy marketing campaign. That's it. There's nothing more to it.
I'll be really curious what the official reviews say after midnight tonight. I might be very alone in my feelings. And I'll be even more curious what some of you guys think.
Sorry guys. I wanted to love it. If nothing else, I hope your experience is better with lower expectations.
Spoiler: 
