What's all the fuss about the nation's biggest carriers coming out with all-you-can-eat price plans?

Verizon Wireless kicked it off on Tuesday when it introduced its game-changing voice and data plans, including one for $100 a month. AT&T followed with a $100 monthly unlimited plan of its own, and T-Mobile USA also announced a $100 unlimited plan that includes SMS and picture messaging.

But Cellular South points out that it has offered an unlimited nationwide plan for voice and data services since October 2007. Its plan includes voice, data and text services for $80 for phones and $100 for PDAs and smartphones.

Cincinnati Bell Wireless also said it has been offering an unlimited rate plan in the greater Cincinnati and Dayton, Ohio, areas since 2004. The carrier says its postpaid and prepaid plans are competitive with the national carriers' recent announcements. Unlimited calling plans start at $100 with the option of adding unlimited text and data/mobile Internet for $15 a month or unlimited BlackBerry Internet for $30 a month, according to the company.

Flat-rate providers such as MetroPCS and Leap Wireless International/Cricket have been offering flat-rate plans for years at far lower prices, although they are regional in nature and don't include roaming.

How many consumers would benefit from unlimited $100 monthly plans? The industry average revenue per user (ARPU) is in the $50 range, after all. Tom Pepe, CEO of Validas, which evaluates consumer's bills, figures 3% to 4% of users he sees would be better off with an unlimited plan because they're heavy users. The typical family on a family plan probably uses 2,100 minutes and pays $139 a month, he says.