If Alien Encounter scared you,
HHN will probably send you running from the park.

Seriously though, HHN can be pretty scary.
The five haunted mazes are the worst, if you feel scared just walking around the streets you may want to skip the mazes. The mazes have you walking through very tight areas that can be very dark and disorienting (fog, strobe lights, loud noises, ect.) There are also numerous scare actors throughout the maze whose sole purpose is to scare the crap out of you. Most of these scares are basically like someone coming up behind you and shouting in your ear, but these types of jolts still scare a lot of people.
The streets are all pretty much the same thing only there is more space, and the actor to people ratio is smaller.
It really isn't that scary to me anymore because I have been to 6 different HHNs, but my first couple times I got pretty scared.