I think the art was done well and I would rate the story higher if not for the anime terrible ending. >< It wasn't really 'terrible' but more or less disappointing and unsatisfactory. But then again, most anime madeup endings are irritating.
Also I think one of the greatest points of Nabari No Ou is its characters. They're fundamentally unique and the main protagonist, Miharu, has a very original personality compared to the usual main characters of action anime/manga. The other characters are charms as well with there own quirks and pasts.
Nabari No Ou is also quite a moving tale about an indifferent boy with an unknown past who becomes livelier over time because of an influence from someone just like him. "Another me" as quoted from himself.
I'm sure the majority of people who watch this anime will enjoy it.
