Story: 9/10
It was absolutely unpredictable for me. Maybe, people who watched OVA can find some spoilers in it, but I think that scenario is great. It's quite interesting story about hurting, friendship and parallel world. Actually, "Black Rock Shooter" has two or even three parallel plots.
Art: 10/10
Fantastic graphic. Each episode was really incredible from graphical point of wvew. Both real and parallel worlds are painted carefully and stylish, that means, in two different styles.
Sound: 9/10
I don't know what to say about it. Maybe, I put nine for sound because I saw the "Puella Magi Madoka Magica", where sound work was really outstanding. There sound is also good, but not the best I seen ever.
Character: 8/10
Many characters, many feelings... How to write about it without spoilers or foolish speculations? Each schoolgirl has each own personality, and each teacher also. Practically all characters are connected together.
Enjoyment: 7/10
Battles is the only enjoyment there, because other parts of this series are very serious and sad. But... are enjoyment main for you?
Overall: 9/10
The "Black Rock Shooter" was expected to be catching, but nobody expected so catching eight-episodes anime. You need to watch it (of course, if you are ready not only to see but also to think).