In the performance brakes world, there is a small amount of debate about the benefits of cryogenically treating rotors, with most people believing that cryo treating rotors greatly improves their durability. An example from Frozen Rotors (one of the leading suppliers) states:
What does cryogenic treating do for my rotors?
Cryogenic treating will increase the useable life of your rotors by 100% to 300% and typically increase the life of your brake pads by 10% - 50%.
To make a long story short, the debate in automotive forums is mainly over exactly what cryo treating does, not even if it has an effect at all. One popular example is that many people believe that cryo treating greatly extends rotor life at the expense of pad life, which is directly counter to the manufacturer claims as above. Another popular claim is that there is no difference for the stresses introduced in daily driving and is not worth the cost, while others quickly counter; swearing it extended their life greatly on a daily driver and is worth the premium.
Finding hard evidence for any claims at all is incredibly difficult. Is there any data out there that will shed some light on this topic?