Apple has officially launched its App Store, an online marketplace built into iTunes and integrated with Apple’s forthcoming iPhone 3G and iPhone 2.0 software update. The store boasts 500 applications, 125 of which are free. While some iPhone users are already downloading applications, it’s not yet easy to do. The reason: While the App Store is live, presumably to provide access to new 3G iPhone owners immediately following their purchases in whatever time zone they happen to be located, most of the world has not yet been able to buy a new 3G iPhone.