I am using the shadow matte successfully but have encountered that certain things I want to extract or do simply don't seem possible... here is the issues;
Assuming I am using the same scene as you do on the documentation (the car on the road)
1 - I want to get the AOVs for the reflections on the floor... how?
2 - If the car emits sparks (which are emissive), why don't they affect the shadow matte?
3 - Is there the concept of "illuminator" like in Mental Ray (wow... now that is a weird moment referencing the crazy slow MR) Basically the lights of the car should illuminate the projected background, the shadows, etc...
Thanks.