are just like any other profession, there are good ones, bad ones, and then there are snake oyl salesmen, that give the profession a bad rap. Find a good one, and they can literally change your life for the better. But, anyone who goes to one needs to realize, it took your back, or neck, or whatever is hurting you awhile to get bad enough to visit them. And, it will most likely take more than one or two visits to really get everything back aligned to the point it stays there, and the pain goes away.
Now, that being said, I HAVE had times when they "cracked" my spine when things were really bad, and the relief WAS somewhat instantaneous. But, that is not the norm, it usually takes a little while.