Well, I tried that once... Just cause I was curious about Dvorak since it's theoretically a faster layout for typing.
I just changed my keyboard mappings to Dvorak and went through a tutorial... I didn't get too far, it was hard to break my Qwerty habits.  You could type quite a few common words using the keys near home row though, so that was cool.
It's a good security measure though.  Switch the keyboard mappings to Dvorak, learn them and memorize them.. and no one will be able to use your box easily 
