No I'm not going to slate the character. He was by far my favorite in this movie. Hiddleston brought a subtlety in his portrayal on Loki that goes well with the hammy and arrogant Thor of Hemsworth.
Loki is a compelling villain in such a way you sympathize with him and somehow know where he's coming from. He lies, manipulates, betrays ... but he a much more complex villain - I for one felt that he's not entirely evil.
Most may not agree with me but I find the story of Loki's fall to be much more compelling that Thor's. This could be because of the more serious and darker tone on Loki's story.
Maybe I'm being nit-picky here, but Loki is supposed to be a god of mischief and unfortunately I didn't get that vibe. In the posters Hiddleston smile look somewhat mischievous and upped my expectation on seeing this side of Loki. There was nothing wrong with the portrayal of the charming manipulative liar because Loki is all that ... yet I wanted to see the 'sometimes but not always harmless trouble-maker' too - the one whom everyone knows to be the root of mischief and mayhem and frustrating as he may be they let him be - perhaps because he's good at talking his way out of trouble or perhaps they think him harmless.
Overall I like the movie but it's not in the same league as Iron man or Nolan's Batman. It's a fun popcorn movie but not one I'd go see a second time around.