Well, just a few things are edited. A few instances of nudity here and there, really, until Volume "7" (due to DH's messing up of volumes...). The scene with Hiroko loses a few panels, and the scene with the evil bully chick gets a page and some panels cut out. She's also wearing underwear and is NOT having sex with her brother.
That's about it. Dark Horse didn't do too much after that, so...
...the whole series is pretty... dark... in the darkest sense of the word. S'alright, though.