Here are a couple of requests that spring to mind:
1. Vary stroke widths over length - shape layers are amazing to animate with, if you could vary the stroke widths so paths tail out or have sharp ends that would make them even more powerful. In fact any additional controls on shape layers would be good to achieve more unique looking effects.
2. On the Fill effect, allow an option for opacity on original - sure I could always just duplicate the layer and and toggle the opacity to see the layer below but it would be nice to have it in the same effect.
3. Invert colours on Ramp effect - just a simple switch to be able to quickly reverse the colours around on this effect would help.
That would certainly add to what is already a fantastic product.