After reading the article and related comments, I bought one "off the contract" AT&T iPhone 4s from apple retail store on Sunday. After connecting to iTunes with an AT&T sim card in, the message "Congratulations your iPhone has been unlocked" popped up. I subsequently switched the Sim card to one from China Mobile, which is also activated for international use. I got a bunch of text msgs from the carriers after a short moment of searching. Then I called a friend in China using the unlocked iPhone 4s, it went through and the quality was great.