I’ve had my TomTom Car Kit for the iPhone for some time now and have been quite pleased with it. The enhanced GPS signal does work really well and it manages to get a lock really quickly. The handsfree calling does work, but not if the road is noisy. I thought the kit came with a FM transmitter, it doesn’t, it comes with an audio out port. Quite useless for a car with no audio in!
My main concern now though is compatibility with the iPhone 4. It does click in, but you wouldn’t want to do it too often. However even if you do click it in, there is no connection made with the Car Kit, so no charging and I guess no enhanced GPS.
You can , according to the internet tubes, add some padding that will allow it to work, but not tried that yet.
I would like TomTom to offer upgrades to an iPhone 4 model or even free upgrades would be nice.