Shock buffs are most useful in IPSC competition pistols of the race gun variety, i.e. in Open and Limited classes. They come in handy when setting up a gun to run with as little muzzle flip as possible. We use low weight recoil springs, FLGRs, shock buffs, light hammer springs etc. until the gun runs as flat as you can imagine. Buffs can certainly cause problems and we change them a lot. Barnhart once had a gun set up with several buffs so the slide would only come back the minimum distance necessary to cycle.
On PD guns, you might consider putting one in when going to the range for some heavy practice. As in most things, there are no hard and fast rules, only lots of opinions. Most opinions seem to come from reading or talking rather than DOING.
