[g_sawchuk]

I would presume quite a bit.
Last year just a drive train could score points - yet we still saw robots choosing to play defense, selecting defensive play over offensive play. This year there is no clear way for *just* a drive train to score points in FIRST STEAMworks (albeit it is quite easy to build a simple scoring robot). The raised lower goal makes it so that you can't push game pieces into the goal, and the gear needs to be raised to be scored - it doesn't appear to be able to be pushed onto the peg.
Considering that you score gears and balls on the same side, this allows for a single robot to play concentrated, multi-purpose defense. While the dividers may make gear defense a bit harder (similar to STRONGHOLD batter shot defense, the robot could just go one way, force you close to the divider, bolt the other way, and you'd take too long to get out).
Gears appear to take some precision to be scored, so a robot should be able to easily hinder your scoring ability in the area - and that's slowing down some massive points.
With the 5 second rule in the key I expect that we will also see some shot defense, but the most likely case is that most defense will occur near the airships to slow down gear cycles.