I don't often preorder, but when I do it's because I know I won't regret my purchase, and I know I want a physical copy to arrive on day 1. Of course I know there's some risk, but if I felt a game really was that risky then I would wait, I just buy the ones I feel are safe bets.
I know what developers and series I like, and if one of my favorite games is getting a sequel I know I'm playing it. Even if the sequel isn't quite as good as the prior game I liked, they're never bad enough for me to not want to play them at all.
I suppose it helps that my tastes lie far enough outside the kinds of mainstream AAA games that are prone to totally botched launches that I've never been truly burned.