The click wheel is a very good interface, especially when you are very often setting a scalar value (volume, temperature, fan speed, etc) or navigating a linear list (songs, contact names, call history, etc) and using one hand without looking at that hand. So it's a good fit for both MP3 players and cars.
Not so good for typing, but can be quite good when there's a good UI that narrows down options for you at each entered letter.
It really isn't for me, it's much easier with the T9-style 3 letters per key on a physical keypad and then up/down on the steering wheel.
Some cars have a click wheel that lets you set letters one at a time, which also works well.
What doesn't work well at all is typing with one hand on a centre console touchscreen.