Apple has just released iOS 4.2.1 GM for developers. So, if you are registered as a developer, you can head to Apple Developer Center and download iOS 4.2.1 GM for iPad, iPod Touch and iPhone. This release is strictly for developers and requires a UDID to be installed on the device.
Apple released iOS 4.2 GM 2 last week and final version of iOS 4.2 is also scheduled to be released this month.
amr 
