iOS 6 is unveiled by Apple at WWDC 2012. iOS 6 has lots of improved features like facebook integration, Siri for iPad, FaceTime over 3G, new privacy controls and lot more features.
Today apple released iOS 6 Beta 2 for developers. This update is available for iOS 6 users via OTA update (Settings > General > Software Update). Now when you update you will see spinning gears while download is in progress (Seriously its cool.). Estimated file size for OTA update is 299 MB.