iPad owners have had to sit idly by for too long as long-awaited features–multitasking key among them–came to the other gadgets in the iOS family. But today, Apple officially released iOS 4.2, which brings not only multitasking but homescreen folders, AirPlay, Game Center, a unified inbox, and other key features to the iPad. This isn’t an ordinary firmware update: It really makes the iPad into a different and much more capable device.

Basically, iOS 4.2 gives the iPad the features previously exclusive to the iPhone 4. Those include multitasking, Game Center (an Xbox Live type of social gaming service), homescreen folders (for grouping apps together, saving screen space), a unified email inbox, AirPlay (to beam, for example, video files directly from an iPad to an Apple TV), and AirPrint (which, well, prints). This update also frees the “Find My iPhone/iPad” security feature from MobileMe, making it available for free to iPhone 4, iPad, and iPod Touch (4th generation) users.

iOS 4.2 for iPad has been available as a beta release for a couple of months, but the vast majority of iPad owners will only make the leap today. And it’ll make a huge difference: The iPad as originally released was very limited in its ability to function as a legitimate computer replacement. Multitasking sounds like one of those features, like cut and paste, that nerds make a big deal about but which isn’t really a dealbreaker to the general public. But it’s not: The ability to have third-party applications running in the background is a key part of actual modern computing, one that will swiftly become indispensable to iPad owners.

All that talk about being able to replace low-powered computers (like netbooks) with tablets–that’s actually possible now, where it was sort of uncomfortable and limiting before.

The update is available now for free from iTunes.