To understand Ravenloft, and perhaps to give my critique of it a more appreciative cast I think it's first important to look at the Hickman's adventure design in general. My long running game set aboard the HMS Apollyon attempted to have horror elements, though perhaps failed in that regard, and with that in mind I find myself looking at the first really successful horror themed D&D module - I6 Ravenloft, -written in 1983 by Tracy and Laura Hickman, a few years after two other modules I've reviewed here (somewhat unfavorably): Rahasia (1979 republished/rewritten 1984) and Pharaoh (1980), but before the couple launched into Dragonlance.
I'm not sure if this is a review or a mediation on adventure design principles, but I've recently been thinking a bit about the horror genre and tabletop adventures - while running a location based wilderness point-crawl with a post-apocalyptic high fantasy setting.