So far so good
Have only used once, so no long term opinion yet. I knocked the rating down a star because the trays were a little bit of a pain to mold to my mouth. One seemed to shrivel up too much on a back tooth and now it doesn't quite have a good fit. Also, there seemed to be a lot of excess above-gum plastic that had to be cut off if the mold. We will see how it pans out after using for a while. I started out only using for 15 minutes and will build up as I normally have sensitive teeth. The first use was not unpleasant, and my teeth did not hurt afterwards.
Rating: 4 stars