I've recently been neglecting my duties in the movie review area, but as it's the weekend and some people might consider it, it's worth posting a review.
Anyway, the story is that sometime in the future, around 2020-something, the mutants and the good bits of humanity are being destroyed by some sentinels that can defeat mutants. So, the way to fix this is a bit of time travel back to the 1970s to stop an event happening and fix the future.
And it's pretty good. The writing is solid. Like the best of the X-Men movies it doesn't shy away from exploring the consequences of such a situation (how would non-mutants react to mutants and vice versa). The same stellar cast from X-Men First Class are back as Professor X, Magneto and Mystique (James McAvoy, Michael Fassbender and Jennifer Lawrence). It manages a few 1970s-era jokes without overloading on them.
I'm not sure I'd spend the extra on 3D, though. I don't mind 3D (Gravity and Avatar are better with it) but there's only one scene where I felt like it might have lost some effect (and it's a piece of joyful silliness that I'm not going to give away).