Ok, just got back from seeing it.
The first 2/3 of the movie, is great beside one thing.
Epic background of the villain, awesome special effects, funny jokes. Many Asgard gods, especially Loki's character was further developed and there were sacrifices.
Spoiler:
However, I don't think the Malekith and Frigga scene makes sense. He could detect the Aether from like, light years away? And he knew it was on Padme even though nobody told him. Even if he could still get tricked, why would he have to waste time to ask her about where is Padme after the trick was over? He could easily sense her and she was not far away. Also it was very stupid to kill her, she could be a very valuable hostage to be used against Asgard.
The last 1/3 of the story is crap.
Spoiler:
I believe after such a awesome 2/3, we were expecting a big, epic, intense final confrontation between Thor and the Dark Elves, but we got a comedic, stupid fight, Malekith was so weak before he got the Aether, and after he got it he was still only having slight advantage over Thor, thus makes the final battle a bit less interesting, since we saw his lieutenant could beat the crap out of Thor. They made the same mistake of MoS, let the NO.2 villain overshadowed the antagonist.And they were just keep getting teleported to different places and could barely keep fight. Thor even had to take a metro to go back. This really damaged the intensity of the battle. and not to say, the comedic couple's scenes further dropped the seriousness of the battle. I also don't understand how could that couple and Padme escape unharmed with a bunch of dark elves behind their asses? We saw they could match the strength of the Asgard warriors, and their weapon is very deadly, especially those "dark hole grenades".
Overall, because of the strength of the villain, the stupid teleport scenes damaged the intensity, the comedic scenes and the "dumb dark elves" made this final battle(supposed to be very intense the serious) a big disappointment.
I don't see the need to bring Loki back to life either, this actually made his sacrifice and selflessness much less precious, unless they are trying to make him play a villain role in the future.
The mid-credit scene is quite interesting.
Spoiler:
Thanos is collecting the gems.