I was just converting some XFrog bushes to tgo, and rendering preview images (so I can easily pick which I need later on), when I decided to try something I read about a while ago.
Someone achieved realistic lighting by adding a second envirolight and setting it to Ambient Occlusion, while the first envirolight was still in Global Illumination.
I tried and below is my result.
Just a simple, basic scene. Only extra nodes to default is 3 XFrog buxus objects and an extra envirolight (with default settings of 1 for all sliders).
The first is only GI, the second is GI+AO, the last one is only AO. GI+AO gives the best result as it's a bit lighter and thus has a bit more detail.