I feel the need to weigh in on this reliability situation with my experience from the manufacturing sector.
Tesla has many things going for it, but one relatively under-appreciated one is the rate of improvement in their change management process.
Based on circumstantial data from multiple sources, including the Musk biography, WaitButWhy posts and many Musk interviews, I believe Tesla is highly responsive to making manufacturing and part quality adjustments. Where most manufacturing is bogged down in lengthy change review processes, I think the Tesla engineering culture moves to analyze and improve failure points much faster than traditional auto manufacturing.
This won't every be completely evident in the short term, as it will only become clear once long term data is analyzed. It manifests in the short term due to a lot of owners driving some of the original 2012-2013 models that are many generations behind parts and processes in use today. I think the 2012 and 2013 Model S's are relative dinosaurs compared to the 2015 cars. They just look the same from the outside.
TL;DR, Tesla has remarkable speed of innovation and improvement in manufacturing process and supply chain, and this will become evident as the 2014, 2015 cars become 2-3 years old. Just nothing to be done in the short term but hold.