;D I'm testing out my computer with populations. What do you think of this one?
The lighting is a little off. I would add a second sun up higher and opposite the visible sun to add some light. Maybe 0.35 for the strength and no shadows.
Njeneb's suggestion is good and fast. If you have patience you can also get an accurate good lighting by increasing the GI detail and sampling, say like GI detail @ 2 and sampling at 3 or 4. Very important is that when objects are in the shadow that the atmosphere samples also need to be upped, because objects tend to get noisy easily.
I like to try easy first. Martin's suggestion is probably the better way to get great lighting. But honestly, I suck at using GI. :P