I always like when Apple listens to customer feedback. With the launch of OS 4.1, the switch on the side of the iPad went from a lock switch to a volume switch. This really came into play when showing photos and passing an iPad or trying to read a book while laying down in bed. Sure you could access the switch through the voodoo magic of double tapping buttons, swiping, and finding an icon (Street Fighter II was easier). But now, the switch works again as expected... just go to preferences and change its behavior.
|iPad Side Switch
Silent or screen rotation lock