said by airtouch25:True a chunk of that is roaming and in those areas there is likely no high speed wireless network and service quality levels are not guaranteed but this applies to AT&T too.
Who cares about data? T-Mo's reliance on roaming translates into dropped calls whenever you move between networks. I loved T-Mobile for tooling around my hometown but I had to deal with dropped calls almost every single time I took a road trip with them.
I don't know if this is a limitation of GSM vs CDMA (it never happens on Verizon when I wind up on a roaming partner, those calls hand off seamlessly) or something specific to T-Mo but it was extremely annoying.