Won't be a problem. They can have fair use policies for unlimited data but otherwise it'll be the same as using it at home.

Of course it is a problem. I pay for 10gb a month but go on holiday for say two weeks and only have 2gb available precisely when I'm likely to need most of my allowance. I get charged a ridiculous rate for each GB after that. This is a big improvement but is not the end of roaming as it is currently advertised.