This stuff really works! One of our cats had a UTI recently which resulted in him peeing on the carpet and in his carrier on the way to the vet. It works best on fresh stains/accidents but it works on old stains too (those might need more than one application).
Our cat carrier was so, so stinky even after we tried washing it out. But we sprayed it down with Purrfect Potion and it's like new again after a day. You can see it working instantly (esp on carpet) - it foams up on contact and you just leave it alone for 24 hours. That's it! Highly recommended!