i got one on each dog. they have them on every day all day this time of year cause they have this urge to kill the baby chickens and ducks. they've left the adults alone for a couple of years now. but, those smaller ones must look especially tasty. anyways... those collars just straight up work! my dogs are outside all day long while we are at work with access to the chicken coop and sometimes eggs on the ground. they won't touch the chicks, ducklings or those eggs as long as those collars are on. probably be ok now even without them. but, i figure i would rather not chance it just yet.
the other thing they are great for is when you are laying in bed at night and they start barking incessantly at some ghost. it sure is nice to be able to just grab the controller off the night stand and beep em. if its nothing worth while, they will shut the eff up and go lay back down. if its something worthy of barking, they might not be so apt to do so and i know its probably worth getting up for a look see.
on the ball thing... my springer and my boykin ain't never been much for playing fetch. so, i've never bothered to force the issue. cause, frankly, a dog who insists you throw the ball all day gets annoying. they fetch just fine in the field. i am ok if they don't want to do it in the yard 24/7/365. although, you have me thinking now about how nice it would be if i could get them to fetch the golf balls as i hit them rather than having to go pick them all up myself.