I'm seeing more LED's in automotive use like tail lights, so that's a good sign. Seems like they've nailed down a stable driver that can handle voltage fluctuations, like on starting.
Many car LED tail lights are actually refreshed at (I'm guessing) 30Hz or so to keep from overloading the wire - They have a distinct look to them from the low refresh rate.
That's a pretty large range to run a current-driven device (the LED) from a fixed resistor. Most useful applications these days will use constant-current supplies that feed the LED a fixed amount of current as the input voltage changes all over the place.
I've seen a few designs that do not overwhelm in luminosity, but I find most of them to be an outright hazard by partially blinding those in following vehicles.