I was initially going to post this as a comment in Andrew's Aoi Bungaku post, but decided it was substantive enough to expand into its own.
The overall pacing in Shigurui is a lot slower than Texhnolyze, Mushi-shi and Lain, yet is also bizarrely dynamic -- episode two adapts about one chapter of the manga with some added background material to lead up to Kogan's introduction, while episode six adapts an entire volume's worth of material. The whole series is very fractured -- despite the careful direction and writing to create the story's two halves -- which I think is what gives the feeling that the visceral impact is lost when action does occur: the pacing between the fights is so deliberate, and the fights themselves so concise that it takes away from any sort of expected viewing pleasure. Treating the violence and abusive sexuality in such a serious and unpleasant manner is one of the main points and means to show the mentality behind such a culture, and one that isn't far removed from many today. (The manga obviously addresses similar themes, but Yamaguchi also idolizes and stylizes the disturbing violence in a way Hamazaki and Minakami doesn't, resulting in a more sensational work where the appeal is more in the insanity of fights and machismo, and less in the motivation behind the characters and their society. One's response to either medium's portrayal is dependent on what you want out of the story.)
This, along with what few female characters there are, create not only a moral center but also a story of real moral consequence where both sides are shamefully self-destructive and neither justified -- even though Irako's devastating beatdown at the climax of the first half makes us side with the revenge he initiates in the second. Although I love my immoral and gonzo stories as much as any action fan, it is more than necessary to have these kind of works -- otherwise we may desensitize ourselves to disturbing extremes.
As for Madhouse: like any other studio, they're only "dependable" when they use actual auteurs (Kon, Hamazaki, Hosoda, et cetera; I still feel that Yuasa is better when he doesn't have to work with plots). I'd love to see more of Iso's work (unlike Yuasa, I feel that he just has to shave off some rough edges on his writing), and they seem to gather the talented needed for literary adaptions when they need it (Mouryou no Hako, Aoi Bangaku). Despite their obvious creative contraction along with the rest of the market for the past year or so, they're the only studio other than Studio 4°C that interests me in what they're trying to do with the medium.