It can be a good deal so long as you use it. Like anything else, if you don't use it, it can be a waste of money. We don't full time, but we typically camp 50-100 nights per year. With our TT membership, I keep my nightly rates between $11-17/night.
As mentioned, with the zone pass, there is no long term commitment. It truly is year by year.
See if this article helps you decide:
http://www.learntorv.com/2013/06/is-thousand-trails-right-for-you.htmlI also have a variety of other posts on my blog about Thousand Trails. I hope it helps!