I've used this product for about three weeks now, 2-3 times per week. I am very pleased with it's whitening properties - much better than the 7% gel I received from my dentist. I have custom fit trays that my dentist made for me, and so far have not experienced any gum or tooth sensitivity. I've only been leaving the gel on for 15-20 minutes at a time, and taking a couple of days between applications.The instructions that accompany the product are very basic, but it seems with some common sense most anyone would be able to figure it out. Overstock's delivery of the product was, as usual, very quick. I paid over $60.00 for whitening gel from my dentist, which was only a 7% strength and came in four TINY tubes, so this is definitely good value for the money.