I was surprised by how well this worked. Being single these days (hello ladies!) I decided to 'maximise my potential' and get rid of the slight yellow tinge to my teeth (too much coffee if there is such a thing). I read a lot of the mixed reviews and after seeing people leaving poor reviews saying things like 'the mouth guard shriveled up in boiling water' I realised much of these were down to user error. (Hint, the instructions say to let the boiling water cool before putting the mouth guard in it!!)
Also you need a tiny bit of the solution, after 3 treatments there is a significant and noticeable difference to my teeth and I've used about half of one of the three syringes. If I wanted I could probably get my teeth US daytime soap white, but I'm pretty happy to stop where I am and use the kit again in a few months to keep them where they are.
One tweak that will make this kit work much better for you is after moulding the gum shields, cut the tabs off the front. These make it impossible to close your mouth with them in and very hard to use the light. If you cut the tabs off it suddenly all works much better and with a lot less drooling!