After playing around with the illumination baking for a while I couldn't really see what true benefit there was to it.
So I ran a quick test. One small plane & a cube in a GI atmosphere. Both baked to polys to enable the illumination baking.Tracked the camera towards them for a few seconds.

Normal animation setting - after 5 frames - 50mins approximation

Illumination baked(25% quality) - after 5 frames - 2hr20min approximation

The baked version also looked awful because of the low baking threshold. So what is with this illumination baking?
It not going to be any use to me like this!Can someone else maybe try a similar experiment to see if it's just me?