I asked a dozen or so experienced shooters yesterday ....none of them have tried them / a few of them have seen the ads for them on the internet - and thought they were just a novelty. The old tracer loads that Zippy was discussing...a few of the guys said they tried years ago ...but they didn't work very well either.
Consensus was - its a waste of money....and a novelty.
Seeing the shot cloud...??? I don't know / yes, maybe if the light conditions are just right on a cloudy or foggy day - maybe it can be seen ( not by me ) ...unless I were at a fairly significant angle to the shooter ...and then its hard to tell if its behind the target or ahead of it.... Its my opinion that most guys who say they can see the shot cloud / are just guessing...
A pattern board - screw in a full choke ...and check your loads for Point of Impact ...to adjust your gun / then screw in the correct chokes for the range you want, and you can check the patterns your shells are throwing.../ Personally, I think that's way more valuable....
I can't see using these things as a training aid.../ but then I'm old and set in my ways too ...
and my skeet scores yesterday were nothiing to rave about ....93 (24, 22, 23, 24 )......but its about as good as I can do these days...visibility was not very good...or at least, my vision ability, was not very good.