Apple has just pushed final Gold Master version of iOS 4.2 to developers. Only members registered in the iPhone Developer Standard or Enterprise Program. You can go download the GM seed now. Here's some of the new features in the iOS 4.2 GM version.
- AirPlay is back to Youtube
- Bug fixes makes it faster
Download iOS 4.2 GM for iPhone, iPad, iPod touch.
UPDATE: You can upgrade to iOS 4.2 now without need to UDID registration, follow our guide posted here to do so.