Back to the main topic, I will say that in the coaster community, skip the line passes are generally disliked, but there are hardcore enthusiasts who use them from time to time. If you're doing a roller coaster road trip, you normally plan to visit large corporate parks (Six Flags, Cedar Fair, etc) on weekdays, and smaller independent parks on weekends. But sometimes that's not possible and you have to visit a Six Flags or Cedar Fair park on a busy weekend and it's your only day there. If so, it might be a good idea to get a skip the line pass to ensure that you can get all the credits and reride the best stuff.
That scenario can apply to ski areas, but once again, lift lines never reach the length of roller coaster lines. So I don't see demand for Powdr's Fast Tracks product as being nearly as big as it is at amusement parks.
At Killington specifically, they seem to be hiding the fact that this even exists. There's nothing on their social media pages about it. Just a page on the website buried under the "plan your trip" and "premium experiences" tabs. I believe this was implemented on a corporate level, and Killington's management didn't necessarily want it, as in they know there will be massive backlash. It sure is difficult to get any answers out of them.