Sprint is the only major carrier out there with a true unlimited plan. We weren't sure if they were going to offer this plan with the iPhone 4S since the iPhone has been known to be a very heavy data user on the other networks. However, Sprint recently reached out to Engadget and let them know that they will be offering the unlimited plan and it will start at the $69.99 price point.
This puts Sprint in a very unique position and gives them an offering at a great price point that no other carrier can touch. Other carriers (Verizon & AT&T I'm looking at you!) advertise unlimited but they really are not.
You can learn more in our Sprint iPhone Forum area here: http://www.iphoneforums.net/forum/sp...hone-forum-78/
Source: Sprint will offer unlimited data plan for the iPhone 4S -- Engadget