It's not just being able to play dvds. It's also being able to change the navi destination on the go. I think it's ridiculous that they won't allow you to change destinations unless you are parked. It's not like it's a complete distraction, and your passenger could change it.

 

some companies make a cd you stick in the player that rewrites the code, allowing you to play dvd's while driving without having to have a switch or anything.