I think for people who's interested in film as a form of art these movies high value. Both in a artistic and cinematographic way. What outtakes, cuts, music, lightning etc etc do they use to create a reaction or feeling in the audience. Is there any groundbreaking methods? Movies are made not only as entertainment but also as a way of criticizing society. And some directors go way to far in order to do so, but at the same time it's extremely effective. Films that makes you reflect and think, is important.
But for me movies are about entertainment i form of drama, thrillers comedy and action. That doesn't mean it hurts to see a "high culture"(best word I could come up with) movie every now and then.
As for Human Centipede: It's not disturbing at all. It's a terrible terrible C-grade horror movie. And it's not in any way scary nor disgusting. It's just horrible action and a horrible story-line with the worst bond-like villain you'll ever see. I've seen it, and it made me laugh quite a bit. The south park take on it was far worse then the movie itself. Scream and I know what you did last summer is more offensive.