Very sad to say I thought Keira was miscast
I very much enjoy Knightley's work but just didn't buy the reality or depth of her character. More angst or even a little desperation when confronted with the darkness of the music world was really needed to sell this movie and Ruffalo was outstanding. Keira just seemed out of place with a scrunched up nose and laugh as a response to most emotional stimulations.
Still a great actress but the movie could have been so much better.