I have a friend who had 2 Rottweillers and an invisible fence. She paid a ton of money for it and her dogs were always finding holes in the line, or their collars wouldn't work, it was always something. She had the fence people come out to her house a bunch of times. They said everything was fine. She lives in Bend, Oregon, in a rural area.
Both dogs kept getting out and eventually killed some chickens. She was forced by the Humane Society to get rid of one ( a blessing in disguise). She kept the male and he is now a lazy pet. He has no motivation to get out!
I have a 6 foot tall cedar fence around my entire back yard. Reinforced on the bottom with bricks and chicken wire. I still worry that my pups will get out. They are both microchipped but I still worry! They are my babies!
Like Sahara's Mommy said, everyone has their own opinion. I know my pups would see a squirrel and be GONE!!!!