The setting (the Labyrinth proper) is fantastic. Plenty of flavour and quite extensible -- you can easily work in your own homebrew adventures in the same locale. The first section of the main plot (the Chamber of Eyes) is a bit dull, but the second and third sections (the Horned Hold and the Well of Demons) are magnificent. The highlight of the adventure in my opinion are encounters W5 through W9, the ancient tests the players must pass in the Well of Demons, which are wonderful dynamic encounters that mix interesting mechanics and tough decisions with shear awesome flavour. The fourth section (smaller than the others) was decent, but was entirely outshined by the Well. I have played this module once and run all or a significant part of it four times now, and I still enjoy it every time.