How were you planning to 'connect' to the car radio? If you're talking a direct connect, I can see their point re: voltage differences = fried Clie.
I use one of the FM transmitters (available at Walmart, Radio Shack, etc.) with my CD player all the time...never thought about trying it with my MiniJam! With the transmitters, you connect their jack in the headphone jack of your Clie. Then you hand tune your radio to find a weak station (here in Dallas I can no longer find an empty space, so that's the best I can do!) Then tune the transmitter to that station. Voila!
There are lots of things that interfere with the transmission, but since my car stereo has no input jack, it's the best solution I have right now!
(see ya later....)