I just acclimatise everything for an hour, 15 mins closed bag, 15 mins open and then slow adding of tank water, never lost anything yet. I know some do it for a lot longer but comes a point when I think the stress of being in a bag/container outweighs the shock of any water change. Never heard of freshwater dipping unless its to solve a particular problem.
I had Brooklynella on one of my clowns, it was looking pretty poorly so did a 4 minute dip in RO, she was very peaceful the whole time she was in there and she looked immediately better on removing her. A couple of days later she was clear.
I wouldn't hesitate to recommend it as a treatment but wouldn't want to do it as a matter of course, would think the odds of losing a fish due to stress of being caught, stuck in fresh water, caught again and dumped in tank would be greater than the problems solved.
I am running a quarantine tank for my reef tank, only exception is stuff from my LFS Reeftank, if he has £5K of corals in a tank with a fish he has had for over a month in his shop I am prepared to risk it. Wouldn't do it with a normal LFS though, this guy is a one man band who I trust implicitly.