My wife and I are both active pilots (small aircraft up through Lear Jets) and we treat the Model S autopilot exactly the same as an aircraft autopilot.
In fact, the S autopilot works almost exactly the same as one of our aircraft autopilots -- almost like the designer of the S autopilot was a pilot.
For example, you need to do something with your hand(s) when the autopilot is in operation (Model S or aircraft - its the same), so just rest your hand on the wheel. It gives immediate tactile feedback as to what the machine is doing, allows you to "nudge" the machine when appropriate and permits you to takeover when needed.
Use of the autopilot doesn't mean the machine is totally autonomous -- it's an aid that allows you to devote a little time to monitoring the other systems; e,g, weather, music, fuel/energy, navigation and your passengers.
The bottom line is that we think the autopilot and, indeed, the whole Tesla experience is fabulous.
Our Model S is second only to the Lear Jet we flew for 20+ years.