I've used them with good results in my ar15 with 18" ss white oaks spr barrel. the important thing is to take your time, dont rush it, dont skimp on the cleaning, and did i mention take your time? It's a 50 shot process with cleaning routines after each round of 10.
pros:
will reduce copper fouling
you will notice a more consistent feel when running patches
you're barrel will be more consistent (less fliers, more shots between cleanings, less variation between clean and dirty)
cons:
you will most likely need to rework your pet loads
if you use all 5 "grits" you will lengthen your jump to the lands
plan at least one entire afternoon to get through the process
^^^ these were my results, your mileage may vary ^^^
though i will say i had a buddy use the kit on his savage 270wsm, and his results mirrored mine. he had a much more drastic reduction in fouling as his wsm would copper up after only a few rounds before the kit. he'll sit down and shoot a box of 20 between cleanings now.
im very happy with the results on my barrel and am planning to use them on at least one of my bolt guns. if you have a non-hand lapped, non match barrel, i dont think you'd risk much as long as you follow the directions.
if you have a high end barrel to begin with, thats shooting well and not fouling, then don't fix what isn't broke.