Is there anything new in Gen III to use two separate phones without going through the whole menu routine? This is very inconvenient since we both drive the car and are frequently together in the car.
You can set up ("pair") up to four phones in the system - I believe when you start the car, it tries to connect in order (1-4). Once it connects to one, it doesn't try to connect to any others (it can only connect to one at a time.) if it loses the Bluetooth connection (due to your wife getting out of the car, for example), it will start over again, trying to connect to one of the four paired phones.
My wife, my son and I are all paired with Bluetooth. It will pair with the last phone connected. To switch, press the On Hook button then press Connect Phone. It will ask to pair another phone. Press Yes then it brings up the screen with the phones that are paired with the system. Select the phone that you want to pair to and it switches. One you do it a couple of times it will become second nature.