We've visited a number of Harvest Hosts and, if you choose carefully, they can be a great experience. Sounds like what they offer just isn't for everyone.
We have a self-contained Sportsmobile (Ford Transit based).
One first Harvest Host was a vineyard in California. We slept in the vineyard with a beautiful sunset view. We "paid" by enjoying a late afternoon wine tasting.
We've also stayed at a "hobby farm" where we were offered eggs from about 5 different species of bird. An olive oil farm and a sky diving location. There was also the maple syrup farm with a tour and tasting. There was a farm with a range of products, some of which are only legal in some states, was interesting too.. Another highlight was an orchard where we were forced to buy perfectly ripe peaches and other fruit. That was a tough one!
Due to the one night limit, we've found it mostly useful when we are in transit and it can be a challenge to find one in the right place were we can arrive at the right time.
Parking can vary from a nice field to a driveway, so you want to read the reviews and figure out what works for you.
There are (almost always) no services, you need to have water, a bathoom solution and be able to dump and fill elsewhere, but that's true of actual boon docking as well.