Don't be so hard on your hand-drawing; the texturing and the like came out quite fine. Additionally, I like the way you did the floor in squares, and the transparency layer with the wall on the ground floor is a nice touch. I think I'll look around for this tutorial, myself, to give a shot at isometric floor plans.
Outstanding, and very "usable". You're right about inspirational--as a gamemaster I look at this map and instantly want to use it, and get ideas for adventure. Thank you for sharing!!! Keep up the great work.