I got one and only used a handful of times. But the way I reason is like insurance... I hope never having to use it, but would like to have it when needed.
I'd go as far as saying if there are more formats coming out for DC charging and Tesla made more adapters, I'd just get them all (assuming they are as popular as ChadeMo) for the sake of always be able to charge when needed regardless the plug type. And with the plan to go all Tesla (replacing our ICE with CT), it's a no brainer investment.
Sure you can plan your trip and make stops at superchargers... but to be really close to the experience I have with ICE (just go wherever, I'd find a gas station somewhere), I want to be able to "just" find one nearby. And with more and more DC charging stations coming in the next 10yrs, why limit yourself?