For iPhone, iPod Touch, iPad developers you can Download iOS 4.2 Gold Master (GM). Apple didn’t released beta version, but released iOS 4.2 Gold Master (GM) and seeded to developers.

iOS 4.2 iPad New Multitasking

This is some featured that available on iOS 4.2

• AirPlay
  AirPlay is an evolution of Apple's AirTunes system that used to let you stream music between iTunes on Windows or Mac and Apple TV or Airport Express connected speakers. AirPlay takes that to the next level, letting you stream video and pictures as well as music from iPad (or iPhone or iPod touch) and the new 2010 Apple TV.
• AirPrint
  AirPrint is Apple's wireless printing service. By the time it ships, it should be able to send pages to almost any printer on the same Wi-Fi network, or to certain printers directly (HP ePrint have already been announced).
• AVRCP for stereo Bluetooth
  AVRCP Audio/Video Remote Control Protocol for stereo Bluetooth, now you can finally — finally — control volume, skip tracks, and do pretty much anything your stereo Bluetooth headset allows. Unfortunately, at least in my tests, volume changes on the headset don't show up on the iPhone's volume slider — but they do work in both iTunes Store streaming and iPod apps.

And many more. So are you ready Download iOS 4.2 Gold Master (GM)

Image courtesy of Macrumors – deanostetto