Contact shadows are really great. The only thing I wish is that the amount that occluded objects are darkened could be controlled with a parameter (1.0 being full shadowed as they are currently and 0.0 being now shadow. They are a bit full on right now.

I know technically that the object shouldn't let light through and that ambient light should be done with a skylight. But in this case I am using it for leaves and it adds a lot of nice complex shadow detail but can be a bit dark. An intensity would allow the illusion of light transmission through the leaves.