I'll be honest I don't have a dog right now and I've never used an electronic fence. However I think there are many cheaper ways to train the dog IF you have the time and knowlege to do it. I feel that the electronic ones should be for help with training not as a replacement for training. Also there is no subsititute for a physical fence... it's kinda like ####... sure it's a naked woman, but when the power goes out, you turn to your wife!
The electronic fence is not a substitute for training. I know people who claim their dogs are trained not to ever leave the property. When the dog is hit by a car, the inevitable response is "I don't know what happened...he never leaves the property!" Really? Did the car drive up onto your lawn to hit your dog?
It also doesn't keep outside critters off your property, like a real fence may or may not do. It's just a tool to help maintain control over your dog. Once they are trained to the e-fence (and they do have to be taught its limits) most dogs respect it completely, and after the learning process they will virtually never receive a shock from it. In some ways, it's better than a real fence...aside from considerations of cost, time for installation, or esthetics, the dog can't burrow under or leap over an e-fence. My dogs can be running flat out after a rabbit, but they still screech to a smoking stop when they get to the e-fence line, just before the correction hits.
The dogs receive an audible "beep" warning them that they are approaching the border. If they ignore this and continue, they get a correction. It takes very little time to get to the point where the beep alone stops them, and soon enough they stop before reaching even that point. As far as I was able to tell, one of my dogs received 2 corrections, and the other got 3, before they learned to pay heed to the audible warning.
Batteries seem to last about 2 1/2 or 3 months for me. I assume that a dog that requires constant corrections or warnings would eat up batteries a lot faster. The new collars do have a blinking LED low-battery indicator. If you don't notice this, you will start to notice the dogs gradually, over the course of days, moving a bit further out. As soon as you replace the battery, the dog will hear that first beep and get right back into line.
Bottom line: I do own three dogs, they are well-trained and socialized, and I do enjoy the added peace of mind that the electronic fence provides. I feel that it is just about the best money I have ever spent on my dogs' welfare and quality of life.