Jigoku Shoujo is one of those animes where you have to wait for the wonderful treat at the end. As many people have stated and I'm sure any viewer will notice after a few episodes is that this series is VERY repetitive. I would say that there is a reason for it in giving viewers a small taste of the hell Ai has endured for many years.
The music is wonderful, animation is stunning, and the characters are a real treat. Some of Ai's team it was easy to guess where in Japanese mythology they came from and one of them was a really tough one. Don't worry you'll get your answers... by watching ^_^
So if you have the patience this is a very good anime.