It's not the dataroaming itself, that has been possible for very long. The big deal about the agreement is that phone companies can't charge you extra anymore for dataroaming.

I have an unlimited calls/SMS plan with 11.5GB data a month. It costs me EUR45,-. When I travel 40 miles east from where I live my current data plan is no longer valid, and I have to pay EUR3.49 per 100MB/minutes/SMS. Yes, hundred MB. Not thousand. Those charges are insane!