Dark, Darker, The Darkness

So I implemented my first dynamic SSAO. Results are following:

I still need to tweak light intensivity etc. but this SSAO method looks weird to me. Model's edges around the camera frustum aren't shaded, but the rest seems to be alright. Also it's quite expensive for rendering time, I know it's post-process but a geometry is rendered twice. Of course it's possible to do it in one pass, but I need to learn about MRT technique first ;)