You'll likely find the replies to be 50/50 on this one! Many folks can't imagine not having a car, and the freedom to drive where they want to go. They can stop at the store to pick things up on the way (a town car service does this too) or run out to buy things. They can go shopping elsewhere for souvenirs and clothing. They can explore other dining options.
Me, if I'm staying at Disney, no way am I going to even use a car! I leave the driving to them. That's one thing I find wonderful about a Disney vacation.
When staying at a nearby condo, of course I have to have one. Last time I did that, though, was over two years ago. We did 15 nights, and it was a blast! We took our time, didn't always go out other than the pool some days. We did both water parks, plus mini golf (both of the Disney ones).
I have come to really appreciate Magical Express. We land, get on the bus, check in, drop any bags we have with the bell services, and immediately head out to a park (and lunch)! Later, our stuff (if we check bags) is in our room for us! Love it.
Years ago, before ME service, we used to use a town car often. I liked being able to stop and pick up snacks and drinks for the room on the way. Now I love saving that $100 for something else!