Also not an aviation expert, but it looks like airplane autopilots can do everything except taxiing and taking off (they can do landings now I guess, in fact, just looking on Wikipedia it sounds like they are preferred in low visibility situations for some airports, because they have more sensors and the airports have maps/beacons to help them out).

Apparently it also must be engaged above 28000 ft. Imagine if autonomous vehicles were so good that they were required to be used while going at speed on the highway.