The previous Shuttle mission had some three EVAs of six hours duration and a couple since by the ISS crew. This assembly mission will have a lot of EVA, including extensive use of the Canadian Remote Manipulator Arm which has to be moved to a new anchor point. EVA is still far from a routine activity.
Our friend (Joe T) is one of their most experienced EVA guys (their ace, as I understand), he led the training of the two rookies with him.
It is very risky business, lots of improv and little margin for error and they've got a lot of work to do this mission.