This adventure provides you with a very creepy scenario. Okay, essentially it's just a haunted house, but the encounters are very well designed and enforce the feeling. My players became really invested in the story and actually cared for the children.
The provided hook for the adventure is nothing to write home about and the first encounter outside of the house has no bearing on the development whatsoever. Due to this it's easy to place the material in another context, e.g. in a city in your campaign.
The spooky atmosphere is enforced by assigning each player character some kind of role. The player receives hand-outs according to his character's role, so the players don't share the same information.
The monsters are variations of the standard ones in the official Monster Manuals. Thus, we are given the full write-ups for the critters but can't use the online Compendium or Monster Builder to further process the data.
So we have well-designed encounters, a creepy atmosphere, a plethora of well-written hand-outs and lots of spooky special effects (so to say) in a haunted house. Good Little Children Never Grow Up is a sure winner!