The OS update offers new features that will be welcome at work and at home. Nearly five months after Apple rolled out iOS 4 in tandem with the iPhone 4 launch, it has released the latest update for the software that powers its touch-screen lineup: iOS 4.2.1 (along with version 4.1 for the latest-generation Apple TV). The free update is a major milestone for Apple: It finally unifies the iPhone, iPad and iPod Touch so that all are running the same operating system with the same major feature set. The update also adds several key new features.