Check this video out, http://www.youtube.com/watch?v=5mNcnj2l6RE&feature=player_detailpage#t=244s. I couldn't have put it better myself. It's only a little mistake, but it really does need to be 99% accurate for this to not be annoying. If you're dictating a message in a car, where there is quite a bit of background noise, it needs to always be spot on as having to change any text using the keyboard will be frustrating and illegal. This guy pronounces S very clearly and is in very controlled quiet surroundings.