You must be joking. The only place I've ever gotten adequate audio quality from an FM transmitter is in a tunnel more than 1/4 mile long. They're crappy even driving through the middle of nowhere where 9/10 radio stations are noise.
No I'll have to agree with your parent. The N900 FM functionality ( among it's other great advantages ) was pretty good. I used to use it all the time.
I've found it to be somewhat dependent on the FM receiver's quality, although cars with extendable FM antennas are rare nowadays.