Cryotreating should ultimately "relax" the structure of some metals and the assemblies it composes, according to its proponents. Cryotreating and its effects are not bunk, as some are claiming. It is a legitimate technology, with measurable results. But theory and reality in the field are two different things. Its seemingly exotic technology is a savvy method to separate the unwary from his money. It is now often being hapazardly promoted and used by greedy vendors on things and in ways where it offers absolutely no practical benefit.
Cryotreating is now done extensively in audio circles to more exotic NOS vacuum tubes, with audible sonic consequences (to my ears adversely so). A vacuum tube possesses extremely tight manufacturing tolerances and operating specifications that respond to the treatment. But I consider it a waste of money in this example based on the result, and not on the lack of a result.
But I doubt cryotreating would make any difference for the average driver in components with operating tolerances as large as those found in mainstream brake components and spark plugs. I imagine in a bona fide race car, where every split-second counts, it might find some utility in some engine components. But for Joe Blow and his '99 Taurus, it is a complete waste of money.