powering a circuit with USB micro; what to do with unused pins
I've done this before but with a micro USB cable and cables shoved against Vcc and GND, except I also had some eeproms on the board. It worked for a while until I accidentally flashed the more sensitive eeprom. I didn't bother with the other output pins of the USB cable. I also had it plugged into my laptop and as I said it worked fine, the only tricky part was that the connections weren't all that secure.

So yeah, you don't need to connect the other pins for it to work as a 5V, 0.5A power source, if a traditional USB out or wall adapter (5V, more if USB3.0 out or a faster charger).