I pre-ordered an iPhone 6 and upgrading from an iPhone 4S. I've had the 4S for almost 3 years and the only "case" I ever used is the Apple rubber bumper thing that fits around the edges. There are zero scratches and no sign of wear on the device, just on the rubber bumper. Do I need a case for the iPhone 6? Mostly for iPhone 5/5S users, how easily does the aluminium back scratch?