Had them a while ago (I think 2010) and service was non existent south of Pax. Their maps seem to be much more fleshed out now. I know I cant get it at my house, but my phone doesn't have band 12 (700mhz) which is much better for indoors.
I would be interested to hear what someone with a Band 12 capable phone experiences for LTE coverage. I do know if your service is spotty at home T-Mobile will send you an LTE repeater or a router that lets you make phone calls/texts using your home internet.