Great article from Business Insider's Ben Zhang. He is ostensibly reviewing the Model X, but he says the Superchargers are the special sauce.
"Over the past year, we've had the chance to experience electric cars from Tesla's mainstream rivals — Chevrolet and Nissan. While the two have put out very impressive vehicles in the Bolt and the Leaf, neither manufacturer boasts the type of fast-charging network available to Tesla owners.
Even though new-generation electric vehicles deliver enough range to alleviate range anxiety around town, long road trips are still virtually impossible. With the Supercharger network in place, Tesla is able not only to further placate those with fears of running out of juice in everyday driving but also to make multistate road trips a reasonable reality for EV drivers.
In all honesty, the Supercharger is Tesla's greatest advantage."