I've often found when working with 3D terrain, what looks good in a isometric view is hardly noticeable in a top down - you almost always have to over exagerate in order make the hills and mountains appear as such in a top down. This of course all depends on brightness of the light source, shadow values and textures used. Thus I find creating 3D terrain less useful for cartography than creating structures, statues, trees and other 3D objects.

GP