Thanks all! I wasn't expecting so many responses so quickly!
Chris, trees are always tricky. I've done quite a bit of editing of textures in photoshop to give better results depending on the lighting: sometimes you need to desaturate the texture, other times it needs more yellow or red, etc. Terragen is great, using other tools in addition to Terragen increases the scope of what you can do. The softness of the trees could be due to using the Narrow Cubic filter, a tad higher than realistic soft shadows settings, and an opacity fractal on the needles to 'thin them out' in places.
Ulco, you're correct, the terrain has seen some WM treatment.
mHaze, the talus fields are masked by a flow map from the erosion in World Machine when sculpting the terrain.
Martin, I agree talus is cool! I've been inspired by the ones you've made. I agree the yellow sucks...it should have plant objects on it, but it doesn't for some reason. One more thing to figure out!
Thanks, all!