For me, the Roadster literally is mobile therapy.
For years I've had problems with my right shoulder. Round about '05 I had surgery, which partially fixed the shoulder, but it still hurt when I used it too much.
When I got my Roadster my shoulder really, really hurt from driving it (because of the manual steering). I was very worried that I wouldn't be able to use the car after waiting so long (and paying so much) for it. I tried to train myself to use my left arm when turning, but it didn't help much.
After a few weeks, I noticed that it didn't hurt to drive anymore. And, in fact, nothing hurt my shoulder. What had happened was that turning the wheel was acting like physical therapy, and it worked. My shoulder hasn't bothered me since.
So,
I have a medical need for a sports car.