Story: A distressing shonen with various, almost contradictory, moods being switched constantly. It goes from ecchi to tragical in a blink of an eye, and the whole mood feels somewhat nervous. Romance is, of course, the epicenter of it all, and it is a great and complicated story with plenty of twists and turns you can hardly predict. The Future Diary contest idea itself is great, but it feels like we're still missing out on a great piece of the backstory that's never explained. It is not absolutely necessary, though, but I would have definitely preferred to know more about the world and the system that runs it. All in all, it is an amazing story. The only reason why I didn't give it a 10/10 is because it feels a bit religious and mystical to me, which I don't really like.
Animation: Definitely on par with today's animes, without too many visible budget cuts and some beautiful moments. While I've probably got the manga creator, Sakae Esuno to thank for those fittingly designed characters, the team from asread did a great job and the series looks great.
Sound: The only noteworthy song is the first opening which feels like it represents the feelings and the psychological state of the anime more than characters themselves can show. Others openings and endings are mediocre at best, with the in-series soundtrack being fitting to the situation - with elements of thriller, innocent fun, madness, surprise and romance drawn through the whole anime.
Characters: Now, this is something that people will likely be the most biased in the anime about. Yuno and Yukiteru, being the main characters, are constantly judged by us, others and themselves and they often fail to hit the spot. Frankly, Yukiteru is a bit of a crybaby. While time passes, sometimes it just doesn't feel like he's learned anything in the meantime and he constantly fails to accept his situation. Yuno, on the other side, is the strong character, described and depicted in great depth, with mystery and violence on her side. While she's a far more unrealistic character than Yukiteru, I find her easier to sympathize with. Most Diary owners are special in their own way and a lot of them have more than one function in the anime, which I loved. However, they all feel tragical and the whole story has this sorrowful tone to it because of them that stays way after you've watched it.
Overall: A tragical and mad, but well told story, with plenty of twists, character concepts and new ideas, this one has surely earned a spot in my top animes. I do not regret watching it, but would not watch it again for all the tears in the world.
I definitely recommend watching Mirai Nikki Redial after this one. It's a short epilogue in which some things are explained and the plot seems to be finally closed down for good.