I've been interested in getting to know anime better, and Key the Metal Idol is my most recent effort -and it has been an effort. I've heard nothing but good about this series, but I've found it slow moving with lots of tedious, seemingly interminable narrative explication. Much talk, little action. I honestly don't understand what the fuss is about. I'll come back and watch it again sometime. Maybe I'm just not knowledgeable enough about anime to appreciate it.
This is the extended English opening:
SciFi.com likes it: "Key's pacing is exquisite, but the poetic imagery is even more compelling".