It's not that hard of a widget, but the more I use it, the less efferent missile silos are. In lob games, everyone spams statics, which causes everyone to spam artillery. When your team's army consists of primarily artillery, emping the opponents defenses does nothing.
If they had mixed units, the opening can be well worth the cost. I am usually the player who has the mixed units and tries to go around their defenses. I would take this opening in a heartbeat, expectantly if there is an announcement that one was launched. but when I spend my metal on a missile silo/missiles, I don't have that army.
Maybe this will allow a team mate to use missiles, so I can more efficiently use my mixed army.
On the other hand, I made someone resign the other day just by sending 4 emp missiles, stunning their defenses/units. I did not even have time to send my units in.