"While Black Swan did get nominated today for Best Picture, Director, and Actor Oscars, it wasn't nominated for Best Original Screenplay. Does that surprise you?"
Not me. I thought Black Swan was the best new release I've seen in months, the script was very derivative. It took large elements from The Red Shoes, Carrie, Repulsion, and Single White Female.
In the hands of a lesser director the film could've ended up as a somewhat standard thriller.
I still think the script is good - it was very smartly executed.

I agree re derivative nature of plotline and each subplot: we've seen them all before. The combination of them in that setting (ballet) gives the story a distinctive feel.

It's interesting how my college students all love the movie. Perhaps if they had seen antecedent movies like the ones you noted they might realize it's not wholly original. But for them, it flat out works.