I received the first toothbrush kit, which didnt work at all. I called customer service and was told to try reversing the battery positions, as there had been a problem with incorrect markings on some units. I tried this while on the phone, but it still didnt work. The agent promised to personally check the unit before sending a replacement. When I received the replacement it did work, but stopped working after 4 or 5 uses. I didnt want to continue trying this product and was prepared to accept the credit offerred. I said I could use it immediately to purchase a product at the same price I had seen earlier. Instead of having to go through that process, the agent offered to simply make an exchange, and she shipped the new product immediately. Im disappointed in the toothbrush kit, but blown away by the wonderful customer service!