I'm trying out the Beta right now. I was unable to find any caves in my main map which is filled with castles and fairly explored. I tried like hell but the majority of my search lead to the plains and very small mountain ridges.
I decided to make a new map and lucked out with a large mountain very near the starting circle. It seems very stable with no game play or technical issues at all. I've explored 2 caves and overall they are a pleasant addition. I can't tell if there are invisible spawners or if they are unnoticeable... critters just appear sometimes. I am not a fan of the new armor's look. I was honestly hoping to get cursed with lycanthropy but it's fine... I guess. Odin's still my god, for now. It would go a lil ways to put a black feather cape in the game. Something bushy and dark. I'll have to hope back to my main map and abuse the new loot. See if stuff breaks. But it seems stable.