First off, I had success with the shader as well...but with a particular scene that is interpolating shapes in order to create hair, I'm having issues. Just trying to figure out if anyone else is having issues in order to share info.
I've applied the custom shader to a model w/hair. I tried each all three Hair & Fur effect rendering options (buffer/geometry/mr prim). The render changes each time...showing different strands rendered each time..sometimes none. The melanin setting is not doing anything either..
Do you have a simple example scene that shows the problem? It sounds like you're emitting different curves with different numbers of points on each frame.