A while ago, I'd purchased an iRock FM Transmitter (review) to allow me to listen to MP3s in the car, and was disappointed with the results: it had few frequencies and, except in the most rural parts of the country, the car radio could barely pick it up.

When I saw the design of the iRiver transmitter, I figured this would solve the problem: the cigarette lighter adapter, I guessed, would probably not only provide a continuous source of power, but also improve the signal strength by converting the car's electrical system into an antenna. The only downside was the $40 price tag, almost twice what the iRock had cost.

I'm pleased to report this FM transmitter works great. It's able to transmit on almost every FM frequency, the signal is generally nice and clear (and does pretty well even when competing with an encroaching signal) and has three presets so that you can store three different open frequencies on the transmitter (I map one or two to my radio preset buttons). The blue display lights up clearly and lets you see what frequency is being broadcast.

The only rather minor downsides are: (a) There are several frequencies on the bottom of my car's FM radio (in the high 87.X range) which the iRiver neglects. Which is too bad, because these are generally wide open. (b) When the MP3 player is at 2/3rds volume or less, and the track gets quiet for a little while (pauses, quiet speech), the iRiver assumes there's no signal coming in and turns itself off. (c) It takes a while for it to notice when a signal has come back -- several seconds. (d) I can only use it in my car.

I suppose some people should also consider it a minor drawback that it occupies your car's cigarette adapter, but since my Firebird (thoughtfully) comes with two, and I don't smoke anyway (though I sometimes run an AC adaptor on long trips) it's no problem for me.

So all in all, I'd definitely recommend this product. Kudos to the engineers at iRiver. (Desite their sucking up to Microsoft. :-))