Being the most recent anime I've completed, I must say, it was amazing.
Before I watched the series, I honestly expected it to be just another shonen ai with pretty art.
Yeah, I was wrong.
It was a crucible of tension between the lead characters, and the responsibility of saving Area No. 6 was a heart-breaking feat for the person at hand.
I fell IN LOVE the characters, (unf, NEZUMI,) and the show kept me gripped at all points. I was never bored with an episode.
And, the art... oh my goodness. Wonderful.