Claret Blue and Green
There are too many situation-based variables for xG to be a reliable measure of anything but that doesn't bother me. It's the fact that it's becoming an inescapable fad that pisses me off. I'm sure there are people who use crystals and the power of prayer to predict results, but they're not being quoted all the time.
It's very easy to ignore if you don't like it. I'd imagine scouts and managers use it to some degree, along with numerous other stats and then the more traditional method of actually watching players once they have identified targets more specifically.