A while back you might recall I was excited about the iTrip, an FM transmitter for the iPod. Well, I just got mine. The bottom line: it is really cool, and it works well for what it is - but don't buy one.
The iTrip is a really nice product - attractive, simple, and works exactly as advertised. The packaging is cool - very Apple-like, gray and white box, fancy form-fitting plastic, etc. - and the documentation is simple and well-written. It has really good usability, like the fact you don't have to turn it on or off, you just plug it in. The deep blue "transmitting" LED is cool, too. (Not shown in the picture - must have been added later...)
The problem is that the iTrip is exactly what it says - an FM transmitter. I don't know how often you compare sound quality between FM radio and CDs (or MP3s), but there is a big difference. I did comparison testing between FM transmission and a wired connection to my stereo, and it just isn't close. The extra hassle of plugging in a cable is well worth it for the additional sound quality.
The real reason I wanted an iTrip - other than the "cool gadget factor" - was to use it in my car. I have an 11-year old car with a killer stereo (Nakamichi), and it doesn't have any way to plug in an MP3 player. So I use one of those cassette adapters - a device which plugs into the cassette deck and connects external players by pretending to be a cassette. The adapter works surprisingly well, but the cassette interface is analog so there is degradation compared to, say, a CD. Plus you have the wire floating around. So I was hoping with the iTrip I could do away with the adapter. Unfortunately the sound quality of the FM transmission is way worse than the cassette adapter. The lack of clear highs and lows was particularly apparent. The situation in a car is worse than a building, because the FM antenna is outside (in my case, next to the rear trunk). I actually had to hold my iPod in the air to get the best sound - not good. Also, the iTrip depends on choosing a radio frequency which is empty, with no station broadcasting. In a building you can experiment and find one. In a car as you drive around you pick up different stations, and they interfere. In North Los Angeles there are basically no frequencies which are completely unused.
So here's the bottom line: Once you get over being impressed that it works, you'll discover that it doesn't work well enough to be useful.
[ Update: Griffin Technology, the company behind the iTrip, took mine back with no questions asked. So if you think you might like an iTrip - check it out, you can always return it. ]