Im probably gonna get some nasty replies for this....but since Ive asked about my JRT, Snickers, weve bought him one, and it works very well! he wore it for two days, and now i only put it on if he gets outta hand. Now, when I pick it up, hell stop what hes doing and roll over on his back...to show me he knows im in charge. It doesnt have to be worn constantly after hes learned his lesson. another good one, and ive GOT to find one, is to buy a whistle that mimicks the warning sound before the static shock. I believe that it isnt something Id use on most dogs, or constantly, but some circumstances require extreme measures.

Edit: We also use the NILIF program with both of our dogs....the collar is not a training method as much as a suppliment.