This series is all about "cool." The sets, the characters, and the plot all have this great feel to them. The universe this takes place in is pretty close to our own, next to the superpowers. There's just this stylized "I'm-so-cool" feel about it. The art overall matches the mood of the moment, with the colors, characters, sound and "camera" all properly taken advantage of and used to their fullest extent. The action scenes truly shine, but even the dramatic scenes carry the emotion of the story in a very exact manner.
As far as content and viewing age; Geneon gives it a "13 and up" rating, but I would say 16 and up. There are a few intense scenes with violence and blood, and one nudity scene that is put in there just matter-of-factly. It's not sexual, not raunchy, but it is there.