I watched it a few months back.
See, most people probably go into it thinking that it's going to just be another new low for - as Langsta said - "torture ****", which is really a kind of a silly term made up for a lot of modern ultraviolent horror movies that aren't that much different than the exploitation movies from 30 years ago, just with bigger audiences and bigger budgets. But putting "The Human Centipede" alongside those movies is almost kind of an insult to it. I won't argue it to be a grand artistic achievement or anything and I certainly doubt that the guy who made it intended it to be, but it's actually one of the most purely, astonishingly nihilistic movies I've ever seen. Most of the "torture ****" films and franchises at least come with some point, maybe even more strongly pushed messages than the average movie. It's a cautionary warning or faintly philosophical argument, it can be quite stupid (see the "Saw" franchise) but some sense of meaning is usually present. "The Human Centipede" doesn't really seem to have a point. You watch 90 minutes or so of unimaginably horrific scenes and then it ends. No one seems to learn anything or gain any deeper understanding of anything, not the character(s) or the audience. There's no happiness or sadness or love or humanity to it. It's not even exploitation: there's nothing erotic about it for the vast majority of people (hopefully), the violence is surprisingly minimal, and most of the disgustingness is implied or just inherent to the idea. It's nothing for nothing's sake. When Roger Ebert reviewed it he didn't rate it, and basically said that it was one of the few times in his career that he's come across a movie that can't be rated, can't be called "good" or "bad", which you can't tell anyone whether they should or shouldn't see. The only reason to see it is to say that you've seen it, that you've gazed into the abyss or something. It's interesting to see and think about but I have no desire to ever watch it again.
And that's all the serious analysis I can muster about the movie where people have their mouths sewn to other people's *******s.
How about the part where the Japanese guy poops for the first time? "I'm so sorry!" lolololololol
EDIT: torture asteriskasteriskasteriskasterisk