We had good experiences with HH this fall when my wife and I did a six week VA to BC trip and back. We stayed at three HH sites along the way.
At the first, we camped between a nice pasture and a barn in Indiana where the host had his woodcrafting business. Very quiet (except for the occasional owl and coyotes), and we were the only ones there. The second was at an apple orchard in WI on the top of a ridge with a beautiful sunset view of the valley below. Again, it was quiet and we were the only ones there until 5 am when workers arrived to get to work on the apple harvest. Not a problem, as we're early risers. And on the way back through Indiana, we parked next to a barn on an organic farm. This time there were two other campers. One was on his way west after being an exhibitor at Expo East, so he had an interesting rig to look over. The other camper pulled out a guitar and serenaded us with some professional level playing. But again, very quiet after 9 pm.
Of course, you're expected to patronize the business, so we did early Christmas shopping at the woodcrafters, loaded up on apples at the orchard, and filled our fridge with free range eggs and organic cheese at the farm. HH requires you to certify that you have self contained grey water storage, so I added a PVC drain pipe tank to the truck bed before leaving on our trip. But honestly, no one at the sites we visited came to check and see if we were using a grey water bag external to the camper.
We found that Harvest Host was a good alternative to staying at state parks in the midwest where there are few national forests (and almost zero BLM sites) to boondock.
The organic farmer told me that the last few years had been challenging for his farm economically. But he said that since he signed on as a HH host, sales had increased quite a bit, and he was feeling more optimistic about the long term prospects for his farm. So I left feeling that the HH program is beneficial to at least some of the host sites.