I finished the demo couple of days ago.
I feel a little sorry to write this, but in my opinion, story is pretty medium. Maybe I feel like that, because it's only a demo, and I didn't see whole story. Art is pretty good. Menu is well-designed, flying light spots were pleasant surprise for me. Many elements were animated and you can feel the time that developers spent on writing those details. I didn't really pay attention to the music.
Demo isn't bad, but as the Rooke said, it doesn't grab me. If I could judge, I would give some 5-6/10.
I'll probably buy and read full version of game, but I'm not waiting for it like I waited for english version of Grisaia no Kajitsu
Anyway, I recommend that you try the demo