I had an early version of the Model S with the autopilot (P85D). Once it was made available I noticed a DECREASE in the reliability after every update. From day one it was great. It would be glued to the car in front of it and kept me safe. Over the three years I owed it, it only got worse. My theory was that they tried to make the car drive too much like a human. Rather than going safely down the middle of the lane when passing it would try to give a little more space and thus get closer to the median. It only got worse from there. I no longer have the Model S, but it was the best car I ever owned. That said, I won't get another until there are huge improvements to the autopilot.