Dear Christ, Infdev is beautiful. I'd take some pictures of the awesome terrain around my crappy little noobfort if it didn't bring me back to the ESC menu every time I hit printscreen :/
Makes me wonder how he does it.
I use Perlin noise for mountain generation for game heightmaps, with various types of erosion simulation to keep the jaggies down. I wouldn't think that would work for a voxel-based system like this though, especially since there's a much larger dataset...