Using a cell phone while out of the USA

Lately, for some crazy reason, I've found myself, multiple times, in Toronto, Canada, and Willemstad Curaçao. My Sprint phone doesn't work in either place. As luck would have it, my Sprint contract is about to expire and so I am trying to figure out whether I should change carriers.

If you are in the same boat, here are some very handy links that I came across:

From reading these, T-Mobile seems to be the right choice for me and where I live. Do you use T-Mobile? How do you like it?