I had heard that FM transmitters were not as good, so I've been using a cassette adapter (Monster) and it works wonderfully. However, I decided to try out a bluetooth device (Motorola Roadster 2) in my car, which does us an FM transmitter and it works "OK". Scratchy sometimes. But the device gives you the option to locate a better signal.
I am using TuneLink Auto FM transmitters, it's sound quality is also good.The cigarette-lighter-adapter device is among the only FM transmitters that doesn't require cables to use. I am happy with it. So you can make a try of it.