It's not bad. I quite enjoyed it. I won't say it's amazing, but still.
It's set back in the 1960s, with a young Charles Xavier (James McAvoy), still able to walk, as a postgraduate at Oxford (or was it Cambridge? Or some Ivy League US place? Wasn't really paying attention.) His "sister" is Mystique (Jennifer Lawrence, who has been living with him since breaking into his
CIA Agent Moira MacTaggert (Rose Byrne) discovers what Shaw's up to, and drafts Xavier in to help, as an expert on mutants; once the top brass are convinced that such things are real, a new research agency is set up, and Xavier and Erik start recruiting.
There are some interesting aspects to the film. For example, it's explicit that we should frown on everything done by Shaw and team, and that Erik's self-destructive quest for revenge is Not A Good Thing, but the film refrains from commenting on Xavier's creepy use of mind-reading to pick up chicks, or the sinister implications of his casual use of coercion. The film also makes much of how Erik, with his darker approach to things, is also much more accepting of the mutations that are visibly different (which has always been part of Magneto in the earlier films).
(I found myself wondering why Mystique was always choosing to be taking the same form all the time; well, because that's what Jennifer Lawrence looks like. Duh. It's cheaper than the make-up.)
There's a good training sequence in the middle. It isn't just the usual montage; Xavier is portrayed as a teacher, and as someone who helps and encourages. It's interesting that we never see him training, however.
I'm sure that now there's a film that includes Emma Frost, the Interwebs will at last be happy (especially since she spends half the film in underwear, which I gather isn't far from canonical), but personally, I found January Jones' portrayal to be bland.
There are plot holes. During the early sequences with young Erik, there's an obvious sequence of events that just doesn't happen, and the only reason that it doesn't is that it would break events that they want to occur later in the film. Bah. Clumsy. But on the other hand, how Xavier ends up in the wheelchair is quite well done.