ORIGINAL: Missileman
They work sometimes, sometimes not and are a complete waste of money.
They need a good clean horizon to work, clouds or surrounding trees or hills will render them useless.
The FMA Direct Co-pilot is not the same as the AFS found on the Nexstar. Its actually designed as a failsafe, not as an instructional tool. It uses the temperature difference between the sky and the ground to determine attitude of the plane, and must be calibrated for the individual installation. These are actually gaining popularity among the UAV set as a failsafe in the event a UAV loses the connection with the transmitter, and if I recall correctly, it can be set to only restore the plane on a loss of the transmitter signal. It is not easily confused by low sun or clouds (at least as advertised).
Having said all that, I haven't actually purchased one yet, although I am planning on getting one in the next few months for my aerial video plane.
But like others have said, it is NOT a substitute for qualified instruction.
Brad