Trello have been pretty transparent that they would eventually offer some sort of premium package in the future but they kept adding so many free features that it was getting harder to imagine what kind of features they could actually charge for. The features they are charging here are nice but they aren't real game changers and I thought they had already offered some of them (data export, Google integration).
All that being said, I think Trello is a great product and I'm sure they'll pay for more than a few nights at the pub with this new revenue stream!