Anyone else think this ability is pretty useless? Most of the movement impediments are in the corners of the board and rarely ever crossed. And with the Union working best in teams, there are very few times you'll want to be near one unless you're keeping the troopers together.

Cannot agree with you. There are many places on the gameboard where that skill is "a-must-be". Both entry points to the Galleries have "hard terrain" there. That skill will in meny occasions save your "back" - try it a few times.