Though it has been quietly offering its WiMAX 4G mobile broadband service in Atlanta for at least a month, Clearwire Communications LLC officially went public with it this week.

While we don’t know yet if consumers are channeling Scarlett O’Hara (“As God is my witness, I’ll never go Internetless again!”), the CLEAR service is available to nearly 3 million people across approximately 1,200 square miles. Dubbing it “the fastest unwired city in the South,” Clearwire is promising download speeds of 4 to 6mbps with bursts exceeding 15mbps...