Story: The story was engaging and had interesting stories to tell. Yes, it is repetetive, but it gets more interesting as you progress through the story. It's not until after about 5 episodes you get into more suspensful histories and events. It wasn't the most original storyline as some people may say it's the same concept as Death Note, it didn't bother me too much. After 20 episodes, you get more into Enma's history and death. It kept me curious for the entire end of the series. If you watched the first few episodes and thought it'll be the same over and over again, just keep watching. I assure you it'll be worth it.
Animation: I enjoyed the animation and thought it had some special characteristics and differed to most animes. The scenery looks well-done and gives a dark feeling at times when it needs to. I do say that the characters may look very similar from time to time. The characters have quite large, uneven eyes. The animators did give it a sense of realism with this though. I'm happy that middle-schoolers look like middle-schoolers, high-schoolers look like high-schoolers, adults look like adults, etc.
Sound: Usually music doesn't mean much to me. I admit I was expecting a more dark, serious opening. The background music repeats itself from time to time, but it works.
Characters: It's hard to get emotional for the characters after only 20 minutes of screentime. There's still a lot of unanswered questions to the main characters. Some events happening to the characters seem a little forced such as when people hear about the Hell Correspondence website and the tragic events that go along.
I enjoyed the anime and I thought it was well worth it. I think I liked it better than most people thought.