the shadowsense setting works a lot like the anglesense setting for lights.
 it affects how quickly a face becomes dark based on the angle the sunlight2 is hitting it.
 this only has an effect if there are many faces that are on slightly different planes (ie: tri soup terrain).
 on a flat floor, with walls around, shadowsense has very little effect.
 ex:
 
shadowsense 0.0
 shadowsense 0.9
 
 regarding less shadows from main sun, yes, i agree it is an issue.
 the problem is that the fake GI is too dark in general, which means i had to use brighter sunlight2 settings which hides the shadows.
 
 maybe some more tests with higher number of suns with even lower sunlight2 or something may yield better results...