Only seen the first DVD, but quite liked it. Thought it was bloody violent etc, fair enought, but what i really found interesting was that the main character was very... real. He wasn't some square jawed hero, nor the typical anti hero. He was neither chiche, nor anti cliche. Which is rare as often when created the characters come either from a pecreated stock, or a random charactered gernator.
The story also seems to have a few twist and turns ahead, and some fairly obvious things as well.
May rent the rest however giving the less that glowing reviews it seems to have got so far, but since haven't read manga may think more of the anime that those that have seen both.