I was on the verge about getting Planet Explorers. I missed it the first time it went on sale, and this second time around I almost got it... but I finally decided against it. It looks good, but it's not doing anything that Minecraft, Terraria or Starbound aren't doing (well, generally speaking at least). For a 3D Minecraft I guess I could get EverQuest Next Landmark, which seems a bit more involved than PE when it comes to modifying the terrain.
Maybe when it gets out of Early Access and there's more of a game to it, I finally get it.