I have an aux input on my car stereo (thanks to Honda for putting one in at the factory -- I love my Element) so I've been using an iPod in it since I drove it off the dealer's lot. I noticed recently however, I prefer using my iPod shuffle over my 20Gb iPod.
I know it's less music and even less information about that music, but the shuffle mode beats the standard iPod shuffle mode. When I autofill my shuffle randomly from iTunes, I have it pick high rated songs more often, so when it plays, it's not a completely random sampling of my gigs of music like the full sized iPod, it's actually random music plus a bunch of songs I love. This means when I'm driving around 1 in every 4 songs or so are my absolute favorites (I'm miserly with my 5-star ratings) and makes for enjoyable driving. Now I just use the full sized iPod for long trips when I want to go from audiobooks to music or pick specific new albums, otherwise it's all shuffle all the time.
While I'm talking about my shuffle and iPod use, I heartily recommend Matt Webb's thoughts on his shuffle. Like him, I too wish the "next" button was the largest one on the device and I also feel much of the attraction of the blind shuffle playback is in the rediscovery of your own music.