In 3 Tesla's I've owned, voice commands are only 80% accurate. This is with a male midwestern accented (U.S.) English. I can talk with a Texas drawl... if that is necessary, to see if the car gets my speech better.
My wife, on the other hand, thinks voice recognition is a joke, and doesn't even bother trying. Its hard to call voice recognition redundant or helpful to the touch screen.
