I love to travel, and nothing beats being able to land in (pretty much) any country in the world, turn on your phone and have working service just like that. No SIM cards, no different numbers, no local pre-paid cards, and no crazy international fees.
As someone who enjoys work/travel for weeks to months at a time, every other major carrier is not feasible for this (think 10$/day, which becomes unreasonable when you're out of the country for 3+ weeks).
Unless somebody else could recommend another option it seems I'm stuck with T-Mobile for now.