I believe all dogs can benefit from the use of an e-collar, the only difference will be how much each will benefit. The collar itself will not train the dog, it will only give you the ability to hold a dog accountable for its actions at a distance and to correct behavior instantly. At the earliest age of 6 months let the dog wear the collar around for a month. At 7 months you can begin collar conditioning the dog to commands that the dog should already know. Like stated previously, you can ruin a dog with a collar but when used correctly it is very beneficial.
An e-collar is not a short cut way to train but a smart way to train. By being able to correct a dog at the exact time necessary during any circumstance (close, far away, swimming, etc), you are able to limit unnecessary confusion and stress between you and the dog. Why wouldn't you want that?