Using the materialmixer and a few masks I'm mixing 3 materials. Works pretty cool, and there is a nice transitions between the imagemaps. All three make use of a displacement map, and individually they look great. Material mixer looses the displacements, and the result is a not displaced material. When I plugin a displacement into the displacement input of the material mixer node, I only get one displacement visible (duh), and that displacement displaces also the material it's not originated from.