I've been out for a month, and what I have to say is... WOW.
My jaw dropped when I cruised through the new caves, blocks, and generation. Absolutely amazing. The ore retextures I wasn't fond of at first, but then I saw that they were doing it for colorblind people, and I applaud that! The ores contrast against the grimstone looks completely awesome. I've had my issues with Jappa but he has been hitting the ball out of the park.
The ore gen overhauls I'm excited for. Different layers will take time for me to get used to, for sure. Especially since I hate having to dig out shafts; I much prefer spelunking (more so with this update). ...But it brings a totally new dynamic, and provided we mine in the right place we can get even more of an ore than we possibly could previously! And just... LOOK! Mountain mining is going to be a legitimate option!!! Plus, we now have a solid risk/reward for going into the deep dark!
...With that said, I've been looking at the lack of cave biomes in game and the discussion from this and the previous page, and I have a suspicion. ...We may be getting cubic chunks. Or at least a vertical biome system. Either way, I can hardly wait to see the new biomes in game, particularly the lush caves and wherever the sculk will grow. [Crystal caverns?]
We're only just starting to enter spring, and this is slated to come out in the summer. Going by that and of what we know, there is still SO much more to be had. I am so [expletive redacted] excited for this update to come out. This will forever change the game.
Here's to hoping that we get new atmospheric effects and music like in the nether and oceans! [And I hope to see the day red dragons make it in, haha]