Apple is finally acknowledging those battery life issues in some iPhone 5S models, releasing a statement to The New York Times. Apple spokeswoman Teresa Brewer said:
We recently discovered a manufacturing issue affecting a very limited number of iPhone 5S devices that could cause the battery to take longer to charge or result in reduced battery life. We are reaching out to customers with affected phones and will provide them with a replacement phone.
We don't know how many iPhone 5S units have been affected, but it would have to be a decent number if Apple is going to officially address the issue. If you have an issue with your iPhone 5S, at least now you know you're covered. If not, then enjoy your iPhone 5S!