I found this useful as I am running this level of DotMM right now. It has given me some good role playing ideas (language for the gith, who largely don't speak common) and helps drive you towards the cool part of the adventure. Really kind of the extra stuff there isn't room for in the book, but can enhance the player's experience, that I as DM would never have time to sit down and think of. It also helps tie this level to the next one. It's not a must have, but its very useful and I would reccomend it to a DM running the Crystal Labyrinth.
[4 of 5 Stars!]