We've been members for three or four years now. I found out about it before I even owned a TT, and was looking forward to joining as soon as we had an appropriate "self-contained" rig (a requirement for joining.)
We use it often, probably about 6 to 10 nights per year. We love it. We love that we get to see things that we wouldn't otherwise take the time to see. Usually the HH locations are a little off our route, if you just looked at origin-to-destination route-planning. But we've enjoyed getting off the highways a bit. The locations are almost always beautiful and "different." We've enjoyed meeting the people who own and operate the farms and wineries, when we've been able to meet them. When the owners aren't available, the staff is usually very friendly, but it's not as much fun for us as meeting the owners. After the facilities close in the evening it is usually very quiet and peaceful. However, farm life starts early in the morning, and you have to be prepared to hear farm equipment as soon as the sun comes up. Sometimes even earlier.
As far as the purchase is concerned, we tend to spend $20 to $30, which certainly doesn't equate to "free" camping. However, we get the night of camping PLUS whatever we spent the money on. Pretty good deal, as far as I'm concerned.
One of the rules is that you only spend ONE night at a location, unless the owner invites you to stay longer. That one-night rule is the only part I don't like. It means the normal use of HH is when you're on the road and you have an overnight (or overnights in different locations) along the way. It's not a great program for a camping destination.
As you can tell from what I'm saying, this isn't just boondocking. If you're just looking for boondocking, HH probably isn't for you.
-Speak