Are you talking about SSAO in real time in Outerra?
Also, I'm not sure how your shadow system works exactly, and if it is meant for handling a lot of shadows, but do you plan on having tree shadows eventually? I think that would look fantastic! Here is a screenshot of Crysis with dynamic tree shadows:
Or I suppose you could do non-dynamic ones like Oblivion did for their tree shadows. Still looked a whole lot better than none:
EDIT: Though after thinking about it, even if you JUST went with SSAO it would still look pretty darn good since you are just using ambient lighting in the forests right now.
Although SSAO is hard on graphics cards... depending on which system of it you use. I'd still prefer direct shadows.
EDIT2: And because I just KNOW you all want to read more on SSAO and HBAO, I will give you this:
http://www.nvidia.com/object/siggraph-2008-HBAO.html