The combination of being very
fast and having no 'cost' associated with loss (no morale hit, etc.) makes drones excellent 'surprise' weapons. You can use them to strike at some fleet or out-of-the-way planet that would have taken a lot of trouble to attack by ships. If it works, your enemy has gotten a nasty surprise and possibly been thrown off balance while your fleets haven't had to even move, if it doesn't work (powerful defenses were waiting for them) you haven't lost nearly as much as if you'd sent a fleet of actual ships. As a corrolary to this, yeah, they also make good scouts. Just send them in, heck send ONE in, and use combat replay to see what it witnessed before it was smoked.
