No performance engine ECU should take crank position from the camshaft. There is a whole list of ECU's that don't recommend using the CAS for crank position. The AEM works as well as you would expect using this system.
Obviously I'm speaking from 1st hand experiance. I don't know why others don't have any sucess with the AEM, hence my comments.
After a tipoff from a forum member, I've found someone who actually knows about the AEM and has worked with them for over 4 years. I have every confidance with the AEM as long as its in the right hands.