The Explorer PCB is designed to be integrated with the Rover 5 and provides an easy answer for integrating the Arduino with propulsion and various sensors. It integrates with the Rover chassis for power, control of the motors, and for sensing both current draw and the rotary encoders.
It also provides power (3.3v and 5v) and control interfaces for all the servos and sensors that I will need. It also has a battery charger built in to keep the on-board batteries up to power. It has four IR proximity detectors on each corner of the board and is designed to support a pan and tilt sensor platform on the bow. There is also an area for prototyping which I am not sure how or if I will use at this point.
You could accomplish all of this with individual shields but this was an easy decision for me.