This mission will be a milestone for both the station and shuttle as we complete a major phase of the station's assembly.
This mission ... effectively jump-starts us back into assembling the International Space Station.
The crew of this particular mission will attach the heaviest, largest and most complex piece of station hardware launched on the shuttle so far.
There's certainly an element of mission risk. Not safety risk, mission risk.
The shuttle missions that have gone to the station so far have been extremely successful. This mission takes the level of complexity up a notch.