For example functionality has changed for the rotation lock. With the upgrade your rotation lock is now used as a mute button and rotation is accessed via the dock of the iPad by double clicking the home button to view a multitasking bar. Flick from left to right and then tap to lock the screen orientation.
Another new feature is the ability to use a Braille Display with the VoiceOver accessibility function.
A summary of the upgraded features on the iPad are pictured above. For some brief information on the features see Apple iOS 4.2 software upgrade site.
For more detailed information download the Apple iPad user guide for iOS4.2 software.