Crazy good art, must be said even though it's been said many times over.
I like how this is practically a layer to drape over another dungeon / adventure. I love that, and makes it very easy to insert in an ongoing campaign. I think one awesome way to use this module is by implementing it on a location players visited before (and that's dear to their heart), but has been waxified.
I have to keep this one in mind for that scenario :)