You have to remember that T-mo's terms and conditions say that the majority of your usage must be in the US each month. So pulling out the sim just for trips could get you cut off. It also says something about no more of 2 weeks of international use per month. But I have one friend that used it for nearly 6 weeks without issue. He is a long time T-mo user so that might account for that.

List of about 20 or so real world test of T-mo world wide roaming.
http://www.howardforums.com/showthre...Data-Speedtest!