It is a coming of age story unlike you have ever seen before or will see again I am willing to wager. Much has been written on the web and in the media about this, but you have to judge it for yourself. The animation and music (provided mostly by the indie Japanese band The Pillows) are a cut above the rest. I don't think I have enjoyed a soundtrack as much since Cowboy Bebop or Macross Plus.
Gainax, the makers of such animes as Kane Kano, Neon Genesis Evangelion, Wings of Honneamise, and Mahoromatic, shows again why in my opinion why they are the best studio out there in anime. They never seem willing not to push the envelope in what can be done with anime.
One note I would make, this is not really for the younger viewers out there. There is a good seal of sexual overtones through much of the series given the subject matter.
