If you get one, please remember that they do stop working from time to time (thunderstorms sometimes pop the fuse, if you have a power outage you may to reset it from time to time, etc.). We have neighbors with 2 scary dogs that are "contained" by the fence, but they don't check it often after storms, etc. and many times the dogs get out and chase kids, me when running, etc. It's a lawsuit waiting to happen. Not saying your dog is mean, just that these fences aren't 100% fail proof so they need checking to avoid problems with escapees. What happens if you're not home and a storm pops the fuse? Are you certain you dog would stay in the yard or does he/she like to get right up to the fence and "see if it's working?"
You also have to remember that, like other posters have said, some dogs are willing to take the shock to get to whatever it is they want to chase so you have to evaluate your dogs temperment to find out if it is likely to break the fence.
We have another neighbor that has one and she does what I would do: when she's home the dog can run in the fenced part of the yard and do whatever. But when she leaves, she locks it in the garage, just in case she's not there and the dog gets out or the fence goes down.
We looked at them for our dog but decided against it for these reasons plus the fact that we have a lot of wildlife and strays around here that the fence wouldn't keep out.
Just my. 02