Eagle-eyed MacDailyNews reader "GizmoDan" found the following on Apple's "iPhone How To: Cleaning iPhone" page:
To clean iPhone, unplug all cables and turn off iPhone (press and hold the Sleep/ Wake button, then slide the onscreen slider). Then use a soft, slightly damp, lint-free cloth. Avoid getting moisture in openings. Dont use window cleaners, household cleaners, aerosol sprays, solvents, alcohol, ammonia, or abrasives to clean iPhone. If your iPhone has an oleophobic coating on the screen (iPhone 3G S only), simply wipe your iPhones screen with a soft, lint-free cloth to remove oil left by your hands and face.
According to Merriam-Webster, Oleophobic means "having or relating to a lack of strong affinity for oils."
In other words, Apple's new iPhone 3G S's Multi-Touch screen is skin oil repellent*. Less iPhone smudging and wiping is a Very Good Thing.