I have watched all of the currently released episodes (up to ep 19). just some of my general thoughts:
I absolutely love this anime. This is up there with Full Metal Alchemist as my favorite anime of all time. It has an unforgettable, original storyline. I am so glad I started watching this anime.
My favorite thing with this anime is that the animation is the best I have ever seen in an anime. I am also in love with the art style. Everything is beautifully animated.
There is nothing more I could ask for from this anime (except for *SPOILER ALERT* Shun to come back!). It is the most perfect anime I have ever watched, and I can't stop praising it. The bgm is amazing, the animation is amazing, the characters are honest, and overall it is the best anime ever, no exaggeration. The only thing I dislike is how irritating Mamoru was, but it's totally understandable.
This anime has all that I could ever ask for (wow i just can't emphasize that enough, can i): beautiful, honest, serious characters. I never find myself criticizing this anime.
Basically: definitely watch this anime! It has action, romance, slice of life, fantasy, sci fi, mystery, drama, and adventure all in one package.
(also, does anyone have any other recommendations for animes like Shinsekai Yori? thanks!!)