Worth noting that not every country lets you offline a map. There's a list of countries you can offline a map for here: https://support.google.com/gmm/answer/2650347?hl=en
It's a long list, but there's some notable / surprising absences (e.g. Brazil, Spain).
"Unpleasant." What I'd strongly recommend is to download the map using offline maps before you leave. If you wait for Google Maps to download the data over the 2G/free tier you'll be in for a very long (10+ minute) wait.
I did not do offline maps before I left, but mostly we were on tours so we didn't really need them. But if I was e.g. exploring a city or doing something on my own, you'd definitely want to do offline maps if you wanted to use Google Maps on their free tier.