I see the poor things lying about all unwanted most of the time. However, they are fast, quite manouvreable and have an extremely powerful weapon. It's the best weapon for taking out Goliaths and Leviathans. Simply drive around the target in circles firing at it. Of course you need some good driving skills to do that well.
It's also very good for taking down nodes. It can be fired from quite a distance.
Generally you won't want to charge up the weapon but instead fire it as quickly as possible, it doesn't get snagged on scenery so much then.
The Scorpion is among the best weapons against the Manta, because its plasma ribbon will get sucked into the Manta's fans. Even an uncharged shot can kill a Manta. It also decreases the need for accuracy since the ribbon will attract to the enemy.