Hi, we are using ADP1613 to make our Arduino-compatible robots work with 3AAA batteries.
You can see the robots and the DuinoBot board here:
They work, and the MCU does not hang even when the motors are externally blocked.
There is an step-up to provide the logic's 5V and another for the motor's 12V.
At full speed, following a line continuosly, the robots has an autonomy of one hour and half aprox. In classroom it's much more (due to the interrupted use), and when you plug the USB connector to program the robot, the MCU and sensors takes their 5V from there automatically, just like a standard Arduino does.
The schemmatics will be fully published in December/January (that's because we are working on the public documentation and in the site which is still in construction), but if you need them, I can upload something in a few days, or next week.
Regards!
Julián