I drive a cab in San Francisco, and I have used three different FM transmitter devices,
while averaging 130 miles all over the city. This is indeed real-world testing!
The first one I used was the iRoc. This was long before the iTrip came out.
It took 2 AAA batteries and had 88.1, 88.3, 88.5 and 88.7 via a small switch.
It got lots of interference, and sucked batteries like no tommorow.
We're talking new alkalines every two days (!). Then one of the
strereo channels started failing. Needless to say, I didn't get another one.
My next transmitter device was a no-name analog model from Best Buy;
this one was nice because it offered the entire FM range via a rotary tuner,
and it was easy to find matching stations. Another great feature was that
it was powered by the cigarette lighter, and also had a plug to power my
CD walkman. It got much less interference than the iRock, and cost
$10 less, at $20. Over all, a great buy and the lack of batteries was awesome.
When I finally bought my first iPod (23 days before the 5th gen came out, of course),
Comp USA was offering a free car device with purchase, made by iConcepts.
It is a cradle that plugs into the lighter socket and nicely displays the iPod.
The width of the cradle can be adjusted to fit a mini as well. It also has a swivel with adjustable tension.
It has the standard proprietary plug to power the iPod, and has a 4-channel
switch to choose frequencies. This unit is much cleaner sounding over all
than the others, and only very rarely gets interference. This is over virtually
all 49 square miles of SF (!).
While I have not owned an iTrip, it seems there are a lot of people who
complain about iTrip interferenceat least once a night while I'm working.
However, the price is right. I guess you get what you pay for?
Given a choice, I would still use a cassete adapter over any of the FM transmitter devices;
the sound is much cleaner, with much less (if any) of the usual background noise.
Better yet, a faceplate with a mini-plug input would be ideal.