I was very impressed by it. I used to work in the TV/film industry, and I'm always impressed by movies that don't appear to be technical but are. There's a reason "Black Swan" has been nominated for a record number of Golden Globes; it's hard to pull off a subtle, vague, intense, graphic (WAY more than I expected it to be), and technical movie.
If Portman doesn't win something for this, I'm losing all respect for awards shows. That was a crazy role to try to pull off (literally, and figuratively), and she does it with flying colors.
There are movies I had more fun seeing this year ("Burlesque," "Scott Pilgram...," etc.), but nobody seeing this can deny its place in the top five movies of 2010.