I'd have to say that I got into
School Days because of the ending. However, once the story went into full motion after episode 3 or so, I started to forget about watching it for the violence and I actively enjoyed the show. Very, very different than usual high school romance anime. Makoto's character was ironed out so well that I've actually come to deeply loathe him, and Sekai's hypocrisy is obvious it seeps out of her pores. Kotonoha of course was the most pitiful character, but apparently the game depicts her in her own negative light as well, so I guess the writers wanted to give her
some justice by the end.
As for the ending?
Overall, 7/10 perhaps, though I'm bad with simple ratings like this, so it's probably not an accurate evaluation. It was a good story with a good message I think, but got rather crazy at the end and didn't seem to bring justice to each of the three main characters.