Short version: I enjoyed it. Can't say I loved it, but it was fun and worth the price of admission. The special effects are amazing and worth seeing on a big screen. Volume 2 was the perfect subtitle because it felt like the second TPB of a comic.
1. The core plot was a little too paint by numbers. Though it was a well told story with lots of Easter eggs, cool themes and character moments, you knew where it was going by the end of the first act.
Recognizing the familiar plot formula was kind of a bummer. Like I didn't want to see it, but there it was. An otherwise awesome roller coaster ride kept coming to a screeching halt when they had to check the next box off the textbook plot point list.
2. Much of the humor felt forced, mostly due to weird timing. This is the gripe I usually have about the Thor movies. So many laugh lines were so out of place and dropped at such inappropriate times they were more distracting than funny.
In the first film, the humor was a natural part of the action. James Gunn went for whimsical, and succeeded, but still delivered a real story you could immerse yourself in. It was surreal and alien, and still somehow grounded and believable.
In this one, a lot of the jokes feel more like gags, just not as natural. Though it does have the greatest Stan Lee cameo to date.
I am looking forward to Vol. 3, though. I'd happily watch the movie again because if nothing else, it really is a lot of fun.