After downloading the iTrip app from the iTunes store through my computer, I went to my car and had my iPod Touch playing music through the car FM radio in under five minutes. The iTrip app finds empty wavelengths in seconds, and then I stored the best on my radio on one of the push buttons, so that starting listening is a simple matter. The sound is just as good as playing a CD, and considerably better, of course, than listening to FM radio.
I wonder if some of the problems people have had with some of the Griffin iTrip models is something to do with the car or the car radio.
I would strongly recommend this to anyone. Now I can set up a playlist that will play for the whole of a long journey. Great.
Note added later: I still think it's very good, but what I hadn't realised was just how difficult it is to find a wavelength that will be OK for a journey of one or two hundred miles, you very soon move into an area where the wavelength that was empty when you started out comes into use. The list of UK FM transmitters at [...] is a great help, because you can see fairly easily if you're driving from, say, Cambridge to Nottingham, which will be the empty wavelengths for the entire journey. 87.7 FM in this case. The list is 30 pages long, but I've imported it into Excel and re-sorted it, and it's now very easy to use.
But what would be really good would be if the kit could do it for you: detect when a 'real' station is breaking in and switch to another empty wavelength. How about it, Griffin? I'll give you that idea for free.