iLuv is relatively small and thin. Easy to carry around, will fit almost anywhere. Uses standard 3.5mm stereo audio connector. It is in no way iPod specific. I guess it has "i" in the name because every cool device these days has "i" in the name. You can use iLuv with anything. Laptops, MP3 players, Walkmans, CD players, anything standard. And with iPod too. Of course, if your device has non-standard connector (most mobile phones for example) you are out of luck.
It uses AAA batteries, which is not really a good thing. However, given that device is too thin for AA batteries, I'm not going to hold it against it. BTW, may I suggest rechargeables to everybody who bitches about price of AAA batteries. There is a 3V connector on it, so you don't need batteries if you have 12V to 3V adapter for car. I just got iLuv today, so can't really comment on battery life. It's been turned on for the whole afternoon with used batteries (that I pulled out of my old FM transmitter), and it still works.
It covers the full FM frequency range in 0.1 MHz increments. You can set it to virtually any unused FM slot. As far as I can tell, it stays at the dialed frequency and doesn't "pollute" reception of nearby stations (translated, your neighbors will not hate you). However, the range is very limited. You probably want to keep it no more than 10 feet or so from the antenna of your radio. If you are looking into buying it for use in car, this is not a problem. Tested. I placed it at the worst position in car, furthers away from antenna, and the sound quality was still good. If you want to transmit to the room on the other end of a house, you'll be very disappointed. It simply doesn't have enough juice for that.
There's some audible white noise when there's no input signal, but not any worse than some other devices I had in my hands. Don't expect miracles from something in this price range. If you'll be using it in a car (use most folks are buying this devices for), don't worry about it at all. Even if you have very quiet car, you won't notice this at all. On the other hand, if you are audio perfectionist, you'll probably have to spend much more money for something better.
Conclusion. iLuv is no worse then what I read in reviews for most other FM transmitters. It is way better then my old Radio Shack branded one. I got my iLuv from Amazon. Free shipping.