All the navigation controls are on the same part of the body as the screen, so you can do just about everything other than compose a text message without opening the phone up.
Insoo doesn't even have to take the phone out of his pocket to send an SMS. He knows how to slide it open, which buttons to push how many times to reach the "Send SMS" menu option, compose the entire text message, and hit the send button -- all without even looking at the phone.