Unlike the announcement of Apple at “Let’s Talk iPhone “ event Apple has begun selling unlocked iPhone 4S , Apple has announced at October 4th that unlocked iPhone 4S will be available by November but this wasn’t true as we will see below.
According to 9to5mac :
Although Apple says that they will begin selling unlocked, contract-free iPhone 4S units in the United States in November, we have learned otherwise. Select Apple Stores in the United States have begun selling contract-free versions of the iPhone 4S, which our friend Steven Troughton-Smith was able to both verify and purchase.
The contract-free iPhone 4S can be activated by connect it into iTunes , you will see the above message and you are not locked any more. This unlocked iPhone 4S include AT&T SIM card but you can remove it.
Contract free unlocked iPhone 4S prices :
$649 for 16GB
$749 for 32GB
$849 for 64GB
Update: Now you can make iPhone official factory unlock, you can check the details from here