I guess I would end up using my phone over Bluetooth, negating much of the benefit the large touchscreen in the Tesla provides, ending up fiddling with my phone to change songs etc.
People are going to point out the privacy issues inherent in using Android, and I understand the complaint, but Google already knows my speed and location at all times anyway just by virtue of having my phone on me. I don't think Android Auto would have any interaction with the cameras or sensors, since most other cars do not have them, but perhaps others can speak to this.
Regardless, this has really diminished my interest in getting a Tesla.