Okay, it's confirmed, The Constant world seed is bloody awesome! To get the smaller things out of the way first, the nights look really good, and the occasional bits of marble you can find across the surface are a nice touch, also the danger of the dark while easily managed can make you re-think your spelunking and synergizes well with most other feature's in the seed.
Like not looking at a journal causing someone to ing die, or making a wrong turn and almost getting murdered by a pickaxe wielding lunatic