Try it.

I use it with the same polar image distortion as mtmckinley said.

Just grab your HDR image, or HDR sequence, or any decent image with decent white and black point vlaues, and map that to RealFakeGI's color or ambient color and you're good to go

Then, connect the Real Fake GI output to your shaders ambient channel

Make sure your lights ONLY cast shadows.
Otherwise, it messes up your overall light intensity.
(though, sometimes it's not a big deal)

Global Illumination is all around us, inside and out.

If you use it when you render spearate passes of specular, diffuse, etc. it comes in REAL handy for that added extra touch of realism