The advantage to modern auto flight systems is just like the cruise control in your car is that can operate very efficiently making very small corrections. The basic operating is very simple, but really understanding them is much more difficult. As shown by the Koreans --they could use but didn't really understand about the hold mode. The other problem is that you need to actually know how to fly when things don't go perfectly. Apparently the Koreans couldn't do that either. I flew the A 320 for a long time and always told new guys that the magistrate stuff works great so use it, but don't ever completely trust it. It is kind of like flying with a student--never let it put in a position that you can't recover from. Another problem the Koreans had and something they don't teach you in training.