Whether Natalie Portman danced the ballet sequences or not, it does not matter, because not only is this a movie (which means that there will be effects and tricks and that is what viewers should not care about), she is still such a great actress. The movie still has been so remarkable that the kissing scene or Natalie Portman and Mila Kunis is so talked about and there is even talk of a Black Swan diet.
The plot is a little complicated because this is a psychological thriller. If you have never experienced the kind of emotions that Nina experiences in the world of highly competitive ballet dancing world, you may have a hard time appreciating her character. The plot is further complicated with Nina exploring her bisexuality and the intense love-hate relationship with fellow dancer Lily (Mila Kunis).
Just know that not all that is happening to Nina is real; a lot of what happens is all in her head, but that is no reason not to watch this film because Natalie Portman is outstanding.