I signed up for it when I joined Choice -- it's used with the Preferred Hotels.
Since I stayed in one this week, here's my experience: I slapped down the card, and the guy at the desk looked it up. His reply was that I'd get nothing on this stay, but the next time I'd get a room upgrade or something.
If you go to the website and run down the links, you'll get a picture of what the membership is supposed to provide.