Just returned from the Grand Canyon. I know it's not international, but since the thread is about "global data coverage" I figure it qualifies.

I did not know that I could or would need to roam in the US.

I can and did.

I did not know that there was a limit on my US roaming.

There is.

It's 50 MB under my plan.

If you land in a foreign country, you get a text about roaming.

Not so if you roam domestically. My first indication was a text warning me that I had used 80% of my roaming data, followed seconds later by a text that I had used all of my roaming data. Thank you. Good bye!

And I can buy another 50 MB for $15!

Right - 3x the international price for one-tenth of the data.

This really sucked.

https://support.t-mobile.com/docs/DOC-3299