Been using BT with audible app on my android smartphone since getting my early VIN P85 - and that works reasonably well.
However, the lack of smartphone integration in the Model S software means that some operations have to be done on the phone's touchscreen - not with the steering wheel controls or the car's touchscreen - operations like starting the audible app, navigation through the program (skip forward/back, fast forward/reverse), selecting the book/program, and adjusting the volume (the phone's volume affects the volume of the audio sent from the phone to the car). Plus, the car's display of the "now playing" book/program doesn't show current position (at least from android).
While you can avoid these problems by converting/copying the audiobook to a USB drive - the car's software will not maintain position - and doesn't understand chapters/bookmarks, and trying to reposition back to the last heard point can be very time consuming.