I'm a positive reinforcement dog sports competitor competing at advanced levels of many sports. I was totally against "shocking a dog into compliance" and never considered getting an e-collar. However, I recently adopted a digging, chewing, barking, runaway Jack Russell. Having had a Jack Russell in the past, I knew that even 3 hours a day of positive training did not cure him of running off and killing other animals, and he could never be walked off-leash. With the new dog, I decided to try an e-collar to stop the behavior immediately so that I could keep her safe and also have "good" behavior to reward right off the bat.
I did loads of research into different collars and picked the Educator due to its high ratings and features, including 100 levels, a light, a warning tone that can be turned on/off, and even a locator if you lose the remote. I am super happy with this collar. We keep it on a very low level, like a cell phone vibration. Just annoying enough that the dog finds it easier to comply than continue the unwanted behavior. When she complies, we use food treats as a reward. With this collar, I was safely walking her at a county park off-leash just weeks after adoption, with running bunnies near the trail, and she did NOT run after them. I also taught her not to bolt through gates or try to dig out under the fence. It was also great for teaching her not to charge the fence at my neighbor's big dog. After about 8 weeks of daily use, we now only need it for something like a county park walk and she is well behaved about not barking, digging, etc.
The collar is so easy to use, extremely reliable and consistent, and very easy to put on the charger, which I do every night before heading to bed. The collar never "goes off" on its own and is very responsive. The half-mile range works through several floors of my house/basement. I can be in my home office and give her a "zap" for barking in the yard on the far side of the house and a level down. Because she doesn't relate it with me, she thinks her barking caused it, so has pretty much figured that barking doesn't pay. Anyway, I love this collar and highly recommend it.
Forgot to mention that the light feature is really nice. You can basically turn your dog into a flashlight to see where he is at night, or to light up the area while you search for a lost toy at night, etc. Educator really got it right.