As has been widely reported, 4.2 apparently turns the switch on the side of the iPad from a screen rotation lock into a mute switch. Not having 4.2 myself, I can't comment on my direct experience with ...

The easiest way to rotate your iPhone or iPad screen is by physically tilting the device. As long as the Orientation Lock toggle isn't turned on, you can easily switch between Portrait and Landscape ...

It wasn't there in January, but it's sure there now: the iPad seems to have traded its mute switch for a screen rotation lock ahead of its official launch on April 3.