I switched from ATT to T-Mobile. I live in Dallas and have no problems. The only places I find lacking service is middle of the country **** holes (think GCK). You do get domestic roaming, but it is limited (depends on what data plan, but 50-100mb). Once the domestic roaming data is gone, it can only be reset with the next billing cycle. You do still get unlimited voice and text when roaming domestically. As long as you turn roaming data off and use hotel WiFi it won't eat all your data.

What really sold me (besides being cheaper) is the international aspects of their plan. I spend a lot of time outside the country and don't want to be disconnected or charged a fortune for using my phone. You get unlimited data (at 3g speeds) in about 130 different countries (including Canada and Mexico) as well as unlimited texting. Cellular voice calls are only $0.20/min or you can make unlimited free calls with WiFi calling. WiFi calling is clear and uses your phone and phone number exactly like a normal cell call, only over WiFi instead of cell towers, so you must be on WiFi to use it.

Overall I've been pretty happy with the switch. I haven't noticed an increase in dropped calls over ATT. Data speed is plenty fast. I think they are still expanding their network and filling in some holes so coverage should get better, but I rarely run into a problem as is.

Oh yeah, and the tethering is really nice if you have an ipad or other device.