No problem, other than white iPhone being boaring.
Being boaring, I bought a mirror backside for the iPhone 4S. Installing is a dream! Didn't even have to use ifixit.com.
One problem with any telephone in the summer: Getting HOT! Well, not any more! The mirror rear panel is reflecting the heat as well as the sun. Great fix for overheated iPhones in the summer!! And it looks GREAT!!!