We joined this summer because we were traveling through Vermont and Maine where campgrounds can be very expensive or require too much driving to get to them. We really enjoyed our experiences. We're planning on using them as much as possible, I think it'll be especially good in California because there are so many wineries. Now we just have to develop a taste for wine - :-D! Here's a link to our blog posts about the Harvest Hosts sites where we stayed -
http://rollinginarv-wheelchairtraveling.blogspot.com/search/label/HARVEST%20HOSTS