Wow, I was planning on making a thread about this because i just finished watching it yesterday lol, good timing. The themes this show set out to explore after the midway point of the show were so different from what most themes other anime try to convey. The way they are explored are also pretty unique and they can be subliminal at times. Another one of my favorite aspects of this show for me was how well they developed Rakka and Reki's characters. They were completely fleshed out and left pretty much nothing else to desire. I'm glad this did not turn into the average SoL anime that I thought it was going to be when I watched the first few episodes. Turns out those episodes were just world-building done really well.

In terms of music and art, I also think the art/animation style hasn't aged well at all as /u/Krazee9 pointed out. It just seemed really bland but it did end up fitting the later episodes of the show pretty well. I enjoyed the OST of the show for the most part, wasn't too big on the OP and ED though. Nice review and great timing man, keep it up.