First off, this is quite possibly my favorite anime of all time, but I will not be biased, though my overall score is biased. If I were to rate this anime in an unbiased manner, I would probably give it an 8 or 9. The rest of this review will explain why.
Opening/ Ending themes - 10.
Some of the best out there. They fit the mood really well and play a role in enhancing the experience of watching. I feel that the opening and ending themes of an anime can magnify your attraction to it if they are good enough and the themes in this anime are.
Rest of the soundtrack - 8.
Nothing really stood out for me except for the "sad" song (which made some incredibly emotional moments). The soundtrack certainly doesn't hurt and it can be quite complementary to it, but it is nothing mind blowing.
Story - 9.
I find the basic plot quite intriguing. To put it simply, the relationships between diary holders are quite fragile. If there is cooperation, it is doomed to end in betrayal at some point down the road. This creates a sense of tension, though it is not made nearly as strong as it could have been made (similar to the tension in death note, but very minor). This combined with some "interesting" characters makes for a story that is unpredictable and contains plot twists that you just don't see coming.
Episode Progression - 7.
This category represents the flow of the anime by episode. To put it bluntly, it is quite rough. Some episodes are crazy and full of goodies and other episodes leave you feeling unsatisfied as virtually nothing has happened.
Art - 8.
To be fair, I don't pay much attention to the art. I like some of the color schemes used and a lot of the character expressions, but I wouldn't say that the art stands out or is original/ innovative.
Characters - 9.
I could just say Gasai Yuno and leave it at that, but I will add a bit more. I found that there was a good variety between the characters and aside from Yuki, I didn't particularly dislike any of them. No two characters are the same and you get a sense of individuality with each of them. Not all of the characters have depth, but a good number gain some through flashbacks. The anime does a good job at using the characters to create anticipation for future episodes (mainly Yuno, but Akise is a very mysterious minor character).
Character connection - 10.
There are a lot of flashbacks in this anime. It can be frustrating when you want the main plot to continue, but it really improves the experience as a whole. Most of the flashbacks give you a peek at the past of the diary holders and you find out their motives for becoming god, giving you an idea about the type of people they are. These flashbacks make it easy to be emotionally invested in some of the diary holders and can make some of the scenes heartbreaking. I can assure you that there will be at least one scene where you will want to cry.
Character development - 9.
Aside from a few characters, they don't really change. There are a few fascinating relationships that characters have though and watching them develop is a treat. I will just throw this out here: a lot of people hate Yuki and I understand, but I wouldn't give up on the anime just because of how annoying Yuki is. He is a main character and that makes him a prime candidate for character development.
Enjoyment - 10.
Ignoring some of the frustrating aspects of this anime, I have found it very rewarding. This is because I am incredibly drawn to the nature of this story. The image of Yuno at the end of the first episode made me fall in love and Yuno is like the Naruto/ Ichigo of this series, but with a vastly superior character. Those who are hooked on the premise will love it and those who aren't are at risk of getting disinterested during a few strings of bland episodes.
Overall - 10.
If you are not immersed in this anime, you will not give it a 10 because it has obvious flaws. However, I think there is quite a bit of appeal and a lot of people will fall in love with it like I have. The anticipation of the development of Yuno and Yuki's relationship keeps the viewer wanting more. Really, what makes this show so amazing is that you know that Yuno or Yuki will have to die for this game to end and as fewer diary holders remain, the suspense of how the game will end keeps building up.
tl;dr
Don't judge this based on your first impressions of Yuki and try to watch at least half the show before writing it off. I get the impression that the end is going to be mind blowing, making the 2nd half superior to the first half.
