Its usually quite tough to get that "crackly dry caked mud rock" look on terrain. Mojo got it to a point, but the interface was hideous to me. Bryce, and TG1, it had to be faked. I'm loving this new TG2.
Here is an image I just rendered in about 12 minutes, using 7 levels of fake stones on top of one another, with the sizes increasing and density decreasing as the layers increase. These bumps and ridges are real. I did use a custom image map for the base texture, but it only adds a slightly varying effect. I tried it without, and it looked about as good.