Where do you live? The reason I ask is because once the AT&T and Cingular merger is going to leave T-Mobile without coverage on the west coast (very complicated process, but TMobile piggybacks off the Cingular antennas on the west coast and Cingular does the same on the TMobile sites in the east to be brief)
Since I work in telecom, and am exposed to these sites every day -I can honestly say that in the NYC area T-Mobile has sites everywhere, but are a headache to deal with. This won't be a problem as a customer, but as someone who does work for another carrier, T-Mobile's sites and business practices suck if you ask me.