The main power of this fruit is to copy other people's abilities and appearances through touching and taking a damage from an attack by the one he needs to copy.
It seems that the user needs to be damaged by the attack from the person he needs to copy thus giving it a big weakness. The user also needs a great concentration in using this ability as seen when Chameleone changes back to his original self whenever he sneezes. Otherwise, the user is affected by the standard Devil Fruit weaknesses.