Hey, we'll be the first to admit that the feats in this book are so.... horrifically overpowered, that not only will they unbalance your game, but could, in the best traditions of the hobby, actually teach you how to summon succubi from the Abyss, make $1,000,000 with almost no work, and/or how you too can make sure your magic missiles hit the darkness.
All in real life.
Seriously folks, these feats shouldn’t be used by anyone, at any time, without really good reasons.
Although, the one exception would be GMs who feel they know what they are doing. These fine folks are, of course, welcomed to find interesting ways to add whatever they want to their games, no matter how horrifically overpowered they might be.