It is definately the tallest set as I have all of the castles built in my garage right now. Crazy I didn't notice that until I read it in this thread?
If you only count occupyable floors it is the tallest by two stories. Many of the other tall castles just have towers with flags at the highest levels.
That being said I hated this castle when it came out, and it started my dark age of almost 10 years. Now that I have rebuilt it and have experienced some of the horrible designs in the KK collection, it has grown on me a little.
The design is unique.
The Fright Knights introduced chains into my lego world. I thank them for that. The inverse red roof slopes are a great decorative element. The telescope and skull that pops up into the crystal ball were great ideas as well. The problems with the overall design have been discussed already by others. Worth mentioning the base of the tower is a thick green plate with grass growing on the third story of the fortress?
With all of its drawbacks the parts in this set are pretty darn useful.
The biggest problem I have with this set is the color schemes are too dramatic for me. The yellow in particular in the castle made it seem less forboding and more cartoony for my taste. Combined with the design made this castle too kidified. As an AFOL it turned me off. The more recent vladeks fortress and skeleton tower use the new dark colors to great affect and are likely what lego strived to accomplish back in 1998.
The minifigs have thier uses and I give this set