Currently T-mobile uses 1.9ghz for voice in the US. ATT uses 870mhz and 1.9ghz for voice. This is a good fit for ATT. ATT is land locked on its spectrum. I see this purchase as nothing more than a Frequency Spectrum grab for ATT. This is will give ATT spectrum in the AWS band and in the 700mhz band (perfect for REAL 4G and not HSPA+).
The T-mobile/ATT company will benefit SPRINT by leaving SPRINT as the lone #3, lower price, option.
<-uses ATT as an Enterprise customer and can only hope this helps in rural areas.