Thanks everybody!
@TU: The render settings are
detail:.9
AA: 8 ray trace objects/atmo on (default settings 1/4 samples)
GI: 2/4
The cloud idea around the far mountain sounds cool, I'll have to mess around and see what happens. Although if you want to play with it as well (I know you're interested in some sort of collaboration) shoot me PM.
@Alcaeru: The rocks poking out of the mountains are part of the terrain, I just limited the tree's slope to allow the rocks to poke through. Also, the trees don't have any transparency, just customized translucency values as part of the leave's default shaders.