I guess I'll chime in here now...
Six years ago, I was thinking about buying some property in northern Michigan. Before I got around to doing that, I went to one of the "Membership" campgrounds in the area where I wanted some land. I sat through their pressure sales and ended up buying in. I didn't do it because of a weekness to the sales tactics, but because after evaluating my plans for a land purchase, I decided the campground was a better choice. Sure it was rather expensive, but it was still cheaper than buying property, getting electric and sewer system installed and paying taxes and insurance every year for only one place to go.
At the time of my purchase, there were two "home" parks and two "associate" parks available to me. Today, there are five "home" parks and two "associate" parks. I can stay at any of these parks for free (except for the yearly maintenance fee, which was frozen at a set price for life). If I use a Coast to Coast system park, it costs me $6/night or $11(I think) for a Good Neighbor Park, which is a public campground that allows Coast to Coast discounts. The newest"home" park is within 20 minutes of my wifes workplace, so now we can camp while she commutes.
The Good Neighbor Parks are a great place to stay, if you want to camp near an attraction like Disney World, in Orlando, Florida. I stayed at a campground there, within a 20 minute drive of Disney, for a week. At the time, it cost me $10/night, which was way cheaper than any other campground in the area. In fact, my wife and I towed the trailer down, then had the kids fly down for the week. Our total expenses for the trip, including fuel, camping, food, a whole lot of attractions and the airline was about $2k. Not bad when you think about hotels in the area costing $125+/night, which could have eaten up half of the $2k.
I'm not trying to convince anyone that this is the best way to go. As you noticed, I made a point of telling you that they try pressuring your decission, so be prepared if you go for the sales pitch.
There are alternative ways to join, as some have mentioned, that can save you a lot of money. I would recommend talking to guys who have used the alternative options, before taking that route, so you know how the system works.
Doc