T-Mobile's free roaming worked great for me when visiting Russia earlier this year. WhatsApp text messages, email, Google and Yandex maps, taxis, schedules etc. were all completely usable. Particularly funny since I was getting good connectivity far in the countryside, in the woods, in the sort of area where in the USA one might expect no coverage from any provider.

Uploading photos was a pain point though, and a major one: 2-5 minutes per image.