The only good thing about the first Movie was that porn-parody of it. Human Sextipede? Or something like that? Well its prolly on Wikipedia somewhere. It has BETTER (!) Plot than the Movie that served as inspiration and actually was more successful than the Human Centipede, at least as far as i have read about it.
I have seen the original Movie though and honestly, it wasnt scary, hell its not even that revolting when you consider the obvious Flaws, like how their Heads are far too high to actually be at the Anus anyway. And by my point it only has two "creepy" Moments, one of which was shown in the Trailer for it. You know, when that Doctor Guy expositions about what he is going to do. And the end when front and end die and the middle one is still alive. That was "creepy" but beyond that, the original had no substance. And from what i just read of the Synopsis, the sequel has even less substance or any form of Plot. Hell A Serbian Film has more plot and actually a underlying Point to it, and the film is actually revolting as fuck.
Just read the Wiki entries on A Serbian Film, that by default should give you nightmares. Still, i'll prolly watch it somehow, either full, reviews of it, or smaller clips to see if there is even anything going on it aside from 1-2 Hours of random stupidity.