I think the number of people in model S or X who want to supercharge to save money is small, but that more people who buy the model 3 will want to maximize savings by using the supercharger as much as possible. I see it regularly when people take advantage of free/unlimited things be it public services or an all you can eat, restaurant. I think there needs to be a disincentive to be in a stall when there is a line up. On long weekends and heavy travel days I think it's worth paying extra to guarantee a spot.
It it would be nice if a new software update would show how many stalls are currently available and forecast to be available at your eta. I think it's coming.
I bet it's only a few years away when auto pilot will pull into the stall for you when it becomes available, then move when done, and hopefully less than 10 years away when the car drops you off, goes and charges itself, then comes to get you.
First off, people, charge at home. With such a huge range, you do NOT need to charge, you car does NOT need to charge while you are out shopping. That is Leaf, Bolt, Spark thinking.
Superchargers are put there for long distance travel. The price of electricity is so small, like less than $10 for a fill up (how much did you used to pay for gas, pray tell??) that it is petty, small, thoughtless to think of running down to the local (what, ten miles away?) to sit for 20 minutes to charge. This computes even worse when you get more cars and they are waiting for stalls. I can't begin to get my mind around the thought processes involved.
Also, as you know, Tesla can tell if some "local" owner starts to charge routinely at a "nearby" charger to "save money", and they have been known to notify them and suggest they leave them for long distance travelers.
I can see Tesla thinking that these large numbers of penny pinched Model 3 owners need to pay by the charge and not have it "free forever". Way to go. Ruin it for everybody. It costs more to bill and collect than it does to supply the service.
My $9 worth. (cost of fill up)
I've already commented on the idea that we need to know how many stalls are occupied. It is worthless information. Cars come and go on average of every 3 minutes. You check the situation 20 miles out. Total change. Doesn't help. Guaranteeing a spot? Right. Who's going to sit there waiting for you to drive in (from 20 miles out). Fat chance.