I quite enjoyed this movie. I know a lot of Norse mythology, and that's because I read the comics first, and wanted to know more about the actual myths. I know that Loki is father to Hela, Jormungandr (the Midgard serpent) and the Fenrir Wolf. I figured out Stan, Jack and the rest had done some creative liberty with their versions, and that for once, didn't bother me. I still loved both of the versions. While I'm no expert on Norse Mythology, I do know what Odin's spear is called, he said humbly bragging...
So this movie rearranges things a bit, but that's OK. It's really fun, suspenseful, funny and dramatic in all the proper places. It also didn't feel overlong, which I applaud (several of the Marvel movies need to be shorn of 20 minutes or so). I'd go see this movie again, in the theater, it was that good. I haven't seen a movie more than once since 2002's Spider-man.
I do wish that Sif and the Warriors Three were more prominent in the movie, and the Midgard Serpent is sadly missing, but that would have made the running time around 3 hours, and we can use them in the next movie. Or better, Sif can show up on Agents of S,H.I.E.L.D. again.
The actors all did well, though I wish En Dwi Gast had been actually blue. There are lots of questions that need answered, now. But go enjoy the movie!