Depends, really.
Not an anime, but in "I'm a Beast", the story is made much, muh more hotter if you could understand what Luma was saying. Without it, its pretty much just another (admittedly well-drawn) hentai. There are also some plot elements that I find squicky -- you generally can't tell if a person is brother and sister in anime unless you knew the story, and no mater how hot they are I'm not too fond of incest.
If, however, the dialogue is nothing but generic moans of porn, I can do without the translation. Dubbed hentai, in particular, is pretty bad on the ears.