I was at HHN this year (and in 1994) and loved it. I actually planned my trip a year in advance in order to attend this.
If you love Halloween and horror movies, you'll get a kick out of this. The park sets up all sorts of haunted attractions and has "scaractors" all over the place. There are also special stage shows and a parade too.
It's a separate ticket event but well worth it, IMO.