Ina Fried, All Things D:

“Today has been gangbusters for T-Mobile,” Chief Marketing Officer Mike Sievert said in a statement to AllThingsD. “We experienced lines out the door this morning at nearly all of our almost 3,000 stores nationwide.”

T-Mobile is offering the iPhone 5 for $99 up front, letting customers pay for it over time, but not locking them into a restrictive contract.