Shinsekai Yori was a refreshing change of pace, especially considering what modern anime has degenerated into. While I really liked the intelligent story and dark ambience, I was held back from loving it by a few annoying flaws.
Like the fact I didn't give a damn about the characters.
Dividing a story into arcs weakens it, and while it was a unique approach to actually view a story unfolding across several periods, the brevity of those periods detached me from the underdeveloped characters. A brief fling isn't enough to establish a connection. They could have made it feel like I was watching Saki grow up, rather than just dropping in at major events like some distant relative I don't actually care about.
And lay-over narration is a lazy approach to cutting scenes and development. I got so goddamn sick of listening to this bitch's older self talk about what was happening like the fucking Wonder Years. If you're going to clog a well written story with detached faceless reminiscing, at least have Bob Saget deliver it. (I now picture Squeeler in a suit after that reference. Adorable.)
Also, the last stretch was not paced consistently with the rest of the series. It turned into some kind of half-assed actiony adventure quest thing, and was needlessly drawn out. There simply wasn't enough suspense to warrant the length of the latter half of the last arc, and it felt like a weak genre-swap until the climax, and then the last episode remembered it was a mystery/drama.
But all those gripes aside, it was still an impressive series, and the writing was easily on par with Dai Sato. The twists, especially, were surprising and well delivered, and given the writing and overall quality, it was really a tough call to score it at merely an 8.