We have one custom muzzleloader that has had the treatment, a fine Rice barrel, and it is slick, nice & easy to clean and shoots well. We never had a chance to prove it before, so, who knows? The friend who made it makes match rifles and has a source for the treatment that is so reasonably priced that there was no reason not to, and he has proven to his satisfaction that it improves a barrel (he is a champ shooter). I have heard some pricing for this that I consider a racket; batches of items are done, not one at a time, so the cost is spread per pound.
IMHO, it wont make a bad barrel good, but it may make a good barrel a little better. You do the math for yourself with the price they pitch you.