I think faster speed and a better camera is a given, but I think the single biggest incentive for people to upgrade to the 5S is that they will offer the base model at 32GB, and the top model with 128GB of space. 16GB has been the base storage since the iPhone 3GS. The iPhone 3G before it had a base of 8GB. It only makes sense for them to increase the base for the 5S because in 2013, 16GB will have been the entry size since 2009. That is 4 years of the same space (or a lifetime in technology). It will immediately target power users who need more than 64GB, and will give those who get the base model immediate satisfaction knowing they have twice the space for the same price as their iPhone 5 counterparts.