Every year at WWDC, the new Objective-C features are almost as exciting to me as the new product announcements. Objective-C is a miserably low-level language, and even small improvements can make big productivity differences. A friend pointed me to this presentation by an Apple engineer explaining how a module system might work in LLVM.
Getting rid of the technical issues and code duplication headers introduce would be wonderful, but having a proper module system for sharing code would be even better. Fingers crossed that this will be announced at WWDC in a few weeks.