I have been a T-Mobile customer for about 5 years. My first phone with them was the Motorola RAZR. I had always been happy with my plan, so I never upgraded phones through them. Instead, I have used phones I purchased second-hand and swapped SIM cards. About a year ago, I bought a used iPhone 2G (Edge) and unlocked/jailbroke it. I had been happily using that along with the T-Zones ($5.99) Internet package that I was grandfathered in with. For the most part, everything worked great.