T-Mobile cannot be classified as one of the best cellular providers in US, nor it had the best coverage in the country. However, it was one of the only 2 service providers which offered GSM mobile services, the other 3 major providers being CDMA players.
AT&T has struck a deal with T-Mobile to buy them for $39 Billion. By agreeing to buy T-Mobile, who is currently an innovative, low cost carrier, AT&T will be eliminating their only competitor running on a network with the same technology as theirs. With all the providers moving to the 4G network, how much of this will have a positive impact on AT&T remains to be seen.
T-Mobile had very aggressive pricing, which AT&T was forced to match all this while. With this deal, AT&T will have a monopoly in the GSM arena. It will be the consumers who will be paying the price if this deal goes through.