And don't forget about HD radio.
I know people that swear by sat radio. People that buy cars because they can listen to Sirius. This makes sense to me if you have a long commute and there is something you like and listen to often. Also keep in mind that satellite radio, unlike free radio and internet radio actually pays license fees for each song they play. I know this because I have a close friend that works at XM.
I personally have adopted the iPod for use when in my car. I like being able to summon up the entire library of <put your band here> any time I like. In my case it would be primarily italian symphonic and british prog these days.
When I'm working with my laptop, listening to AM is very easy for me. I would listen to AM in the car too and have done it using my Treo 650 but it is awkward, plus it keeps my phone from being used as a phone. I can see it likely in the near future that cars will have a built-in internet connection, and this would make listening to internet radio much simpler.
Ultimately what will matter most I suspect is whether or not gov't and regulatory bodies will impose taxes/fees or other restrictions on the internet and broadcasters as to what will and will not survive.