Nice site and thanks for taking the time to detail your process but I am slightly concerned about some of the detail in it, for example:
Because the Raspberry already uses TTL level signals, we don't need the level shifter anymore.
I believe the RasPi uses 3.3V signals for the GPIO UART port and not TTL. Whilst I'm not surprised that the DS2480B IC is happily receiving the 3.3V signal from the RasPi and working properly with it, I am slightly surprised that the 5V signal back from the DS2480B to your RasPi hasn't done some damage. I would perhaps consider using a couple of resistors as a voltage divider to reduce the 5V down to 3V3 to protect the RasPi.
I would also recommend not running digitemp as root using sudo. In order to allow a normal user to access the serial port and therefore use digitemp without needing sudo, simply add that user to the group "tty". To do this for user pi run this command:
sudo usermod -G tty pi