emooney:
But those specs you posted say "Operating Voltage 5V". I guess I'm not sure what the difference is between "Operating Voltage" and "Input Voltage (limits)"
operating voltage refers to what powers the pins on the board, the ATmega processor, etc. The input voltage is what you need to feed it so it can maintain that. Of course when it is fed into the board it is first passed through a voltage regulator, and there are some losses which is why 5V input wont do the job. The exception to the rule is the USB which doesn't go through the voltage regulator so doesn't lose any voltage before being used by the arduino.
Hope that makes sense, Geoff