I love these little things, I often carry a whole flight of them over warrior's even, when in fleets PVP'ing...
Don't bother using them unless you are going to use a whole flight of V, there combined jamming strength isn't worth having one or two.
All 5 however can break lock on most frigates on the first or second attempt, in my experience... Maybe I'm lucky and maybe not.
really useful if you are a baiting ship to keep you alive, or BC's and above.
Basically as mentioned above they are for escaping when things go south, release them and target the ship tackling you, now align to something and spam warp, hopefully they will break lock and you will escape, doesn't always work, but in large fleets it's nice to have insurance. Costs you a few hornets but to be honest I'm considering buying a BPO for them they are so useful.
They can also be used to break up sustained fire, pick the nastiest DPS ship, put them on it, you won't get a jam that often, but jamming that Megathron one time in 10 even can mean the difference on an even score engagement between win and lose, if you can stop their heavy hitter for 10-15 seconds then thats 10-15 seconds DPS your doing they can't.
I've also used them to great success in black ops, both to break locks on ships that point you when you light the covert cyno, and on unsuspecting Falcon pilots who think they are safe if they jam you well actually my friend you may be able to jam me, but my drones set to agressive will jam you too and I don't even need a lock...and a Falcon that can't jam can be scrammed and killed!