Story a bit slow to get on (I fell asleep in the middle of the long episodes a number of times in the beginning) and the first few episodes are a bit formulaic, but then it takes off and before you know it, you're addicted... only to find yourself in withdrawal syndromes by the 12th and last episode.
I wish they had gone faster on the events of the first half of the series, and dwelled a little more towards on the second half... or maintained the same level of complexity and sophistication in the storytelling throughout. I kind of leaves you off at a climax after rushing you through it.
The art is a bit of an acquired taste---but once acquired it does feel new and refreshing.
The characters could be deeper, but I suspect their lightness and playful banter is part of a statement in style.
Overall a very interesting series, probably better suited for the more advanced and curious anime/manga aficionados. Mind not blown but certainly eriched.