[Thanks to everyone who sent this in]
Update: We just got an official statement from T-Mobile, and it's confirmed -- service is down. Here's the statement:
Update 2: All service is now restored, according to the company -- they say about 5 percent of users were affected by the outage, though circumstantial evidence would certainly suggest that the number is higher (especially considering that New York City was one of the dead zones)."T-Mobile customers may be experiencing service disruptions impacting voice and data. Our rapid response teams have been mobilized to restore service as quickly as possible. We will provide updates as more information is available."