The main differences:
A) The Switch and Led ports have been separated into individual ports. Any combination of ports can be used. Each port uses a three pin connector. The center pin is the signal from/to the arduino, and the outer pins are both ground. So the polarity of the connector doesn't matter.
B) The Bluetooth module has been moved to pins 10/11. That eliminates the run/load switch -- easier update operations. Just plug in the usb port and update the code. This does require using the "software serial" port in the code.
