Its one of those hullmods that seems bad right up until you are on the other side of it. Like any missile hullmod its really only worth it on ships that have lots of missiles by default, and those ships tend to have a lot of competing OP interests in the first place, so it can be left by the wayside.
Example: Dominator. 3 Medium missiles isn't bad on a cruiser, but putting 3 harpoons, racks, and eccm is a lot of OP. I usually drop the ECCM: the harpoons are already going to hit destroyers+, especially if I have a missile officer in the ship already boosting maneuverability. However its an essential hullmod for Hurricanes and makes them incredibly deadly.
Using it on Salamanders is just plain mean, though I confess I usually prefer finishers to disablers.