I have the same concern. I have a 2G iPod that I use in the car for listening to podcasts and music. It is extremely easy to change tracks without looking at the unit; I just reach down to where it rests on the console in between the front seats and press down on the right side to depress the "next track" button. My fear is that this won't really be possible with a Touch, as I think you have to press it once to wake it, then swipe in a certain area to unlock, then touch a certain area of the screen to jump to the next track.
Sometimes my iPod likes to play tricks on me by playing a lot of songs I don't want to listen to in a row, so I'm like "next, next, next, next, next... ok, this one's good," but all by feel without looking at it. I think that would be difficult with an iPod Touch. That being said, the Touch looks so cool and apps and ebooks would be so nice that I'll probably just use my current iPod in the car and use a Touch elsewhere.