iOS 4.2 Gold Master, would bear same features as the final version, minus few bugs.
Here is what’s new in iOS 4.2
The update primarily brings Multi-Tasking to iPad, as well as folders and Game Center, bringing all iOS device to same level.
Additionally, 4.2 brings AirPrint wireless printing and AirPlay media streaming to all current-gen devices (not supported on iPhone 3G).
Support for MIDI
One of the great new features of 4.2 that seems to have slipped under the radar. MIDI API’s added in the first 4.2 beta without so much as batting an eye. But now that it’s here I think the importance of the new framework is setting in. Serious musicians may now start to recognize iOS as a real studio tool. The large touch screen of the iPad makes it a pretty powerful controller.
Multiasking Bar: Volume, Airplay control, Backlight adjustment
Apple has added some new controls to the multitasking bar, using which you can now control the volume, brightness, AirPlay output directly from there:
Airplay for Youtube
You can stream sound from inside the YouTube app to AirPlay-connected devices. However, AirPlay for video and Apple TV has not yet been activated.
More Parental Controls, Restrictions
Apple gives you more power to restrict features. It gets so powerful that almost any feature of iOS can be controlled: you name it.
More Icons in Folder
Now iOS allows upto 20 apps per folder.