Just bought my first iPhone on eBay, a 4s factory unlocked. As a T-mobile customer, do I just put the SIM card in and hit the ground running, or do I have to do any configurations to enable data? I know T-mo isn't iPhone-friendly at the moment so 4G speed might be more like 2G/3G, but I'm asking more about configurations than speed. Thanks.
Since you have T-Mobile, you will have to get a Micro Sim to start, and then either search online for the settings or talk to T-Mobile support on how to configure your iPhone for T-Mobile. And yes you will be stuck on 2G/EDGE for Data for now, but I heard that they might make their service iPhone compatible soon.