For the record, I'm not a champion of SPRING AWAKENING. I think it's severely overrated and severely underwritten (and I would have voted for GREY GARDENS), but I can see why it's innovative.
The innovation comes in the form of transcending time and space with the musical numbers. These are kids in 1890's Germany, yet through music, the kids of 100+ years ago are able to communicate their feelings via song to present day people. When a musical number begins, it's not 1890 any more. The singers are floating somewhere in space with their thoughts, showing, clearly, that the feelings of a person are timeless and transcend everything.
Not an innovative notion, but it's ABSOLUTELY an innovative way of telling a story.
"If you are going to do something, do it well. And leave something witchy."
-Charlie Manson