If you use a Smart Cover with your iPad 2, you should be aware of a security issue discovered by 9 to 5 Mac that allows someone to bypass a passcode on the iPad to see whatever was on screen when your iPad was locked. An annoyance if the last app you were in was Plants v. Zombies, but a serious client issue if the last app you were in was Mail or Documents to Go reviewing client documents.
The video below demonstrates the security hole.
Until Apple releases a fix, you can fix this bug by disabling Smart Cover unlocking in Settings.
