I upgraded my rating for Henry Horton from 3 campfires to 4 because how nice the primitive sites are and the two trips down the Duck River which border the park.
If you have kids, there are many things to do. Canoeing, disc golf, regular golf, baseball/softball, horseback riding and there is even a nearby archery range.
Update: 6 July 2008
I have upgraded to a pop-up camper since my first couple of stays at HH. Although the park itself, and the primitive sites, rate a four campground rating, I'm afraid I would have to give the RV campground a very low three campfire rating. I was disappointed how close most the RV sites are and how little undercover there is. The sites are 'short' and if a camper has more than one car, they end up parking along the road next to the site...making it feel very cluttered (the ranger and campground host seem to be OK with this). The angle of the sites, and the way the road curved did not allow for very private camping. Most picnic tables and fire rings are in ackward angles (or behind) the entrance to a camper. A few fire rings are closer to other sites than the one you may be camping in.
I was also disappointed that the campground host allowed campers to pay for a site, put a card on the pole, but then not occupy the site. Most sites I have ever visited (non-reservation sites) you had to occupy the site in order to hold it.
On a high note:
We attended the local town's (Chapel Hill) 4th of July celebration and firework show. I would have to admit, the fireworks was some the best I have seen. Chapel Hill is a very small town, but their firework show was bigger and better than I have seen even in Nashville.