If you're asking "are they nice to stay in" I would say the few that we have used have been excellent.

If you're asking "are they a good investment" I would say no, based on talking to a few of the owners. They typically have a hundred or two hundred spots, all pretty much the same, and any "improvements" you might add won't significantly alter the value. In fact they may lessen it, as the pool of people who want "an outdoor hibachi" or whatever will likely be smaller than those who are just interesting in owning "a spot."

One that we were in was about 2-3 years old, and was about 2/3 sold. That destroyed the owners, who could never price their spots for more than the management company was offering, and because of turnover, the management company sales had stalled at the 2/3 mark, because people kept low-balling their individual slots just to get out. After a couple years in the same place people want to wander, apparently.

And this was a gorgeous park, oceanfront, golf course, blah blah blah. But the owners felt "trapped".