I have a stock ArduCopter frame with ArduCopter 2.0.55. I have enabled the mag, and it's soldered as described in the wiki.
It hovers very stable, and yaw is not drifting. However, when I apply yaw input with the rudder stick, the quad yaws in the wrong direction.
It looks correct in the radio calibration in the mission planner. Moreover, it arms when I move the rudder stick to the right. Hence, I don't think I should reverse the rudder channel.