I have used that on a Mazda 3 and a Lexus RX330, as long as I put the N900 near the dash, either using a phone/gps mount just above the dash or a silicon non-slip pad, the FM transmitter is working very well.
With a car charger and the FM Boost app, it served me well in 10+ hour road trip.

I'm suspecting many people might not have tried all the frequencies to find a good one. In Los Angeles which is jammed with radio stations, only 2 or 3 frequencies work well, once you got that it should work.