I tested in three cars and transmitter worked very well. Much better than my old external belkin transmitter.

Poor in a 2006 Mini Cooper -- not able to find a place in the car that maintains a reasonable level of signal to the in-car radio. More static and drop-outs than AM radio driving across the great plains on blue highways.

Mine works great, on a Zaffy i just put it next to the ashtray and sound great ... no static

Tried it once in a rental car (Citroen something) and it worked very good

The bug is here:

https://bugs.maemo.org/show_bug.cgi?id=6792

The FM transmit power is dropped when the USB is plugged in, for me the following worked around the problem and restored full power.

https://bugs.maemo.org/show_bug.cgi?id=6792#c9

function worthless for me...doesn't work at all in my car plugged in or not (2008 BMW). I think the radio antenna is in the "shark fin" on the roof (meaning steel barrier in the form of the roof between the N900 and the antenna) and the rest of the RF path is exceptionally well shielded...so there ya go. Maybe if i open the sun roof, duct-tape (or "90-mph tape", as is appropriate) the N900 to the roof it might work

Not a huge issue...the car has both aux port and usb port...but it was a little disappointing that this little gadget feature didn't work.

I think the poor range of the fm transmitter can be attributed to two things

1) Power - pushing a stronger signal would drain the battery much faster
2) FM regs - in most countries there is a growing regulation on the fm band and items that use it. Its possible Nokia erred on the side of caution and kept the range low for that reason

Great in my Jeep Liberty
Terrible in my Ford Mustang

Works very well for me. I was also surprised to see that it wasn't a huge drain on the n900 battery either.

It works great in my 96 Jeep while in my shirt pocket. In my 07 Subaru, it is miserable. I think it may have something to do with whether or not the antenna is a whip antenna or embedded in the rear window.