How do you get the displacement to be so smooth?
Not sure what you have problems with. Like I said in the tips.txt, use a low power level for the displacements (2 for the ledges) so you get a big mesh that is easy to manipulate.
When manipulating, select all of the displacements at the same time so you don't create holes.
Use a relatively big radius (like 120) and low distance value (2 or so). Use a lower radius to fix some weird bumps that you might have created accidently. Make sure the mesh lines aren't cramped together and there is at least some visible distance between each. Use the smooth function of the geometry painter to make the top parts of the ledges a bit smoother, but don't overdo it, you don't want it to be flat again.
