No time at the moment to write a proper, considered review - but the bottom line is, ya gotta go and see this movie. I totally loved it. I give it, um, four and half stars. I can think of areas for improvement. One is that January Jones was mediocre as Emma Frost. Maybe we can discuss others if we get a thread going. Overall, though, this movie kicks human and mutant butt. Michael Fassbender totally frakking dominates as a young, angry, and badass version of Magneto, just as Sir Ian McKellen did as a more Silver Age (and badass) version of the character.
The movie, as predicted by all, is very much the story of how Erik became Magneto. But it's much better, IMHO, than the nearest equivalent story you could think of - i.e., how Anakin became Darth Vader (and I'm not especially a hater of the Star Wars prequels).
Setting it at the height of the Cuban Missile Crisis turned out to be a stroke of genius, as did the general James Bond look and feel that the makers went for. Some of the sets are just gorgeous. And if you have any reservations about the radically different continuity from the comics, forget it. Go with the flow and enjoy these versions of the characters.
Unless you're totally out of sympathy with this sort of movie ... grab your popcorn and your ticket with both hands and see it soon.