I've just seen it, and I can't say I was as thrilled with it as Bob was. Portman's performance was terrific (particularly when she transforms at the end of the film, and you realise that her whole performance until that point was simply preparation for that moment). I also liked the way the score was done, and a lot of the camera work. The film is very well made, technically, but it's ultimately an unsatisfying tale.
(mild spoilers follow)
Ambitious perfectionist Nina wants to play the white and black swans flawlessly but she's having trouble with the black swan because she's a frigid closet lesbian. So she develops a split personality, goes insane, starts hallucinating, and has sex with a girl. Or maybe she hallucinates having sex with a girl. Like so much of what happens, it's intentionally left unclear what was real and what wasn't (even after the film has ended). And the result? Nina, by switching between her personalities in the changing room, gives a magnificent performance. And the film ends.
What the f***?
Black Swan takes an interesting premise and goes literally nowhere with it.