Icky psychodrama about a neurotic ballerina (Natalie Portman) who's been cast as the lead in a New York production of Swan Lake in which she is tasked to play both the innocent white swan and her evil twin, the alluring black swan. The story of Black Swan is basically Portman's character's descent into madness, as the pressure of trying to embody the black swan causes her to lose her mind.
Although advance praise is focused on Portman's go-for-broke performance, I've found that most other reviewers have neglected to mention that this is, for all intents and purposes, a horror movie. "Boo!" scenes, slashes of blood, psychological terror - Black Swan has it all, even if some (or all?) of the violence is merely in the twisted imagination of its protagonist. Keep that in mind if you have any desire to see the film but have an aversion to horror.
In any event, I admit that I am not a fan of Darren Aronofsky. I found his first two features Pi and Requiem for a Dream to be overrated and silly. I admired The Wrestler for Mickey Rourke's performance, but was also glad to see the director temper his tendencies toward the pretentious with a new, verite approach that was likely borrowed from the Belgian directing brothers the Dardennes. In Black Swan, Aronofsky reconciles his earlier over-the-top theatrics with his grittier new style, and while it's much better than his first two films, there remains a ridiculousness to Portman's freakouts that you will either accept as the idiosyncratic fears of a ballet dancer or reject as campy, overblown nonsense. It's very much like how your nightmares, when told to a friend, sound a lot less frightening than you remembered them (e.g., "This gigantic eggplant with teeth was chasing me through the cabbage patch!").
In a way, I appreciate Aronofsky for boldly depicting his characters' private terrors in all their outrageousness, regardless of how goofy they come across. It didn't work for me in Requiem, but it did in Black Swan. One thing's for sure: Love it or hate it, the movie ain't boring.