I love my Mophie for the 4S. It let's me not worry about battery life at all during long days of travel. It's fantastic. And if I want to feel stylish, I can just remove the case and go naked for awhile. I haven' t had any trouble with the micro-usb port either and I've had it over a year. The only annoying this is the LEDs that blink while charging at night.
Apparently the LED's dont blink anymore unless you press the button now which is a welcome improvement