Review (2/5): Good idea but poorly executed vials
The little vials of the whitening agent are very poorly designed - I had one that was leaking, and one that the brush portion was stuck in the lid so it couldn't be used (there was just a little "pipe" in the "goo" part). The remaining ones worked but it's very hard to get all of the "goo" out so you end up wasting it - think of a toothpaste tube which was solid plastic and couldn't be squeezed! Once you do get it to come out, the "brush" really just makes the stuff clump and glob up - it doesn't just brush on like you'd expect.
Once you get the chemical out and use the system it works well, but I've lost so much of the chemical to bad packaging that now I need to order another set of vials to finish the treatment. It's not cheap, unfortunately, so I hope that they come up with a better packaging method for future purchasers so there isn't so much wasted whitening agent.