In 1990 when this was released, Battering Ram was the largest "castle" I owned. As such, I always wanted a bigger and better castle.
I spent hours staring at pictures of King's Castle, Knight's Castle, Black Falcon's Fortress, and Black Monarch's Castle. King's Mountain Fortress just gave me something new to hope for in 1990.
In 1990, I was really excited about the ghost, the raised baseplate, the princess, the horse barding, the tree, the jail, the pit, and the overall design.
Today, I think the raised baseplate and the ghost are both kinda dumb and gimmicky, and the design is a bit open and weak. Still, this would be a great parts pack, and I would like to own one someday. 8 minifigs also seems like a decent amount for a castle of this size. I don't really care for crossbows though. They seem to be over-used, and TLC never produced a belt-quiver full of crossbow bolts to go with it.
For all of it's flaws, I still like this better than most castles which came after it. (Except for 6086, which I probably stared at in catalogs longer than any other castle set.)