I definitely noticed a improved difference with my hair the second time I used it two weeks after the first. It's much softer and lighter than before, especially when you follow it up with a leave-in conditioner. It's definitely something you have to regularly use every two weeks or once/twice a month, but the results are worth it.
My only complaint is the scent. While applying it into my hair, the mint is incredibly strong and smells a lot like toothpaste and not in a good way. Fortunately the smell mostly goes away after you rinse it out, leaving a more subtle and pleasant mint scent in your hair.