I switched to this t-mobile plan specifically for the international roaming after 10+ years with AT&T. I can report back that after my first experience using it in Argentina I am very happy with it. The 128k I got was fine for: email, translation apps (including voice translation), whatsapp, maps. Total cost for the week after heavy use: 20 cents, because I answered one phone call.

It wasn't immediately clear that I had to pick a certain carrier. In Buenos Aires, data roaming only worked on Claro of the 3 choices I had, and initially my iphone picked to roam with Movistar. There were brief periods of about 10 minutes where while I was in one location (not moving) with a strong signal that it would suddenly drop to "No Service" and then tell me that I'd have to pick another carrier. That happened about 3 times during the week.

Someone posted this helpful link further up thread to determine which carrier you need to select in each country: http://www.t-mobile.com/Internationa..._RoamWorldwide