Actually saw this in the theater. I think I liked it better than the first movie, which was a surprise. It's rather remarkable how well Marvel has done pulling B- and C-list villains out of its archives as movie Big Bads.
Best parts: Loki's banter, and London getting trashed. (Why does it always have to be New York?)
Worst parts: No way do I buy Natalie Portman as a PhD astrophysicist. And if you keep slapping gods, sweetie, sooner or later one of them is going to slap you back. Also, there seems to be a biiiig unexplained plot hole at the end, which I guess will be addressed in the next movie?
Wait for the very, very end of the credits - the audience that waited for the first easter egg and left missed the second.