Bests & Worsts Reviews from Amazon

I bought 8 of these as a Christmas present for my spouse. I was confident this would be a great purchase thanks to the many good reviews. Now I'm wondering how many reviews were "plants." Used a pan for the first time today. It warped as soon as it touched the preheated oven rack!! The sheet itself was room temperature, so there was no unreasonable thermal shock. This is completely unacceptable. I suppose the other 7 sheets will do the same thing. I'm very disappointed with my purchase. Seems that Amazon reviews aren't much more than initial impressions of products and borderline useless.