I watched this movie last night, and LOVED it!! For many reasons. It's about music, and it's about what music means to you as an individual, and it's about choosing to do your own thing. And the music was really quite fantastic; I certainly never knew Keira Knightley could sing, but her voice is distinct and lovely. The acting was excellent as well - seriously, compare the Mark Ruffalo from, say, 13 Going On 30 to the Mark Ruffalo in this movie. Same actor, completely different characters, and that's what I love about good acting. I love this movie, and the soundtrack, and I'm sure you will, too.
Also, major style inspiration from Keira Knightley.