In the wrong hands it can be punitive, but it's absolutely necessary to hunt over a strong willed dog and if judiciously used is perfectly humane.
Only commands I enforce with the collar are "come", "sit", and "take it" (force fetch). The first two are first and foremost safety issues.
I have never burned my dog (held the button down) only nicked her (a momentary correction). She is now a joy to field trial (of course electronic collars aren't permitted on the field during competition) and I can't remember the last time I actually had to use it.
Good post about shock collars. It isn't any more punitive than a leash correction if not overdone... it's the only kind of leash that works on a hunting dog.
You can imagine better than many here, my embarrassment with other hunters when Logan took off to join their party, interested in their sexy German Shorthair, not their birds.
Or when he'd get up and mount the Golden next to him while in his 3 minute sit-stay for his CDX.
Purchasing his remote trainer was the best thing I ever did, surpassed only by finally neutering him . ;~D
However, it's the wrong tool to use on a dominant dog to correct aggression.