Oh I really like the day/night cycle, and the cloud effect looks great - gives the background a real sense of scale. The wind tunnels are easy enough to go through backwards with ball teleporting, but the wall parts do seem to be unbreakable (I had to try).
Bug: after you interact with the cave rift, you can get stuck in some animations by rolling into a ball or flying during the delay before the dialogue boxes appear. Closing the dialogue fixes it, so it's just a small visual bug.