I was first really stoked about the new layer parenting system. I was disappointed when I realized that it really does not work properly.
If I keframe lipsync for multiple frames of my characters mouth, then parent the mouth layer to the head layer I expect that all of the mouth frames on the mouth layer will inherit the rotation of the head layer.
I found that this was not the case. Only the mouth keyframe at the current frame where I rotated the head will rotate. all the others will remain in place.
That is not how layer parenting works. Every frame in the layer is suppose to inherit the rotation, not just one.