T-Mobile's coverage is its biggest weakness. That's why T-Mobile is transparent when it comes to their network.... They show you exactly where their coverage is and where it isn't ( http://compass.t-mobile.com
). They give you a 14 day return window and lock you into only a one year contract. The offer by far the cheaper plans and 'award winning" customer service. (To be honest, if T-Mobile is the best according to JD power, I'd can't even fathom the rest of the industry....)
My 7100t call & data roams on to Cingular whenever I visit my dad in the Souther tier of Upstate NY.