Yosuga no Sora was quite good, but only the last two episodes really mattered, since almost everyone watched it for the incest.
As for the Grisaia anime; from what I've read (Seventhstyle, anime forums, etc.), the expectations are really low. Maybe because it's hard to produce an anime with just one storyline, that's adapted from a visual novel with more than one storyline, and each storyline being unique and adding up to other storylines aka. routes.
I, myself, must say that my expectations aren't that high either. It probably will fail, but I really hope for a miracle to happen and it becoming almost as good as the visual novel.