I really like Hack Sign so far. I have the first DVD and have watched 3 out of the five first episodes.
So far, it's also one of the "cleanest" animes I've personally seen: moderate violence, no language aside from "baka" in the sub, no sex even implied at all, no fanservice beyond the I Dream Of Jeannie-ish costumes for two female characters (Mimiru and Lady Subaru), and a very deep plot and storyline. -^.^-
However, the casual viewer would NOT know this by the opening theme. The theme lyrics, all in Engrish by See-Saw, are utter fanservice bordering on total smut. >.< They're so bad I can't post them here, lest I get banned (however, they can easily be found at animelyrics.com).