I also had no problem roaming in Canada. Also, it's easy enough to go to the t-mobile account page again and change the setting. Tim Horton's has free wifi if Internet access is a problem while the roaming isn't functioning. But I've experienced problems with poor data service and went into the carrier selection page and fooled around with which carrier to select, so that's always something to try if somebody is having roaming problems.

There's also another thread about a universal portable wifi called mypokefi, and if it works well, it's a great solution. Not everybody is satisfied with the speed they're getting in every place they've tried to use it, but it looks very convenient, particularly if you have t-mobile roaming as a backup.