I thought I had responded with updated thoughts earlier... But wow. Just wow.
I am thoroughly pleased with the new batch of content. The music, particularly the disc, is nothing short of fantastic. Despite my initial qualms with the maker not being C418, I adore all the new music coming in. The ambience... Of my goodness the ambience is awesome. The new basalt delta is magnificent, we FINALLY got broken nether portals as structures, and at long last the bastions are here and they are impressive!
And what's this? Chains? As in... Chain armor and chain links for minecarts?
All in all I am quite happy with the update. We could do with another mob--one that goes outside Mojang's obsession with bipeds--but it'll do. Can hardly wait to reset my nether and play with this new set of features! Well done Mojang.