on my e90 i used voice dialing about once a day.
and i am also not a native english speaker (dutch) but it works almost 100% accurate!

the only place i use voice dial is in my car and nowhere else but there it is so handy. just press the dial button the the steerking wheel or a headset, call the name and it dials.

normally in my car the N900 is on the charger and because of that it is even way more dangerous to get my phone in my hands because of the wires.
dont forget that there are a lot of persons constantly in the car and the most calls they make is in the car.