Positives: The extra scenarios are good to have for those days when you just don't feel like setting up your own board. These also give more ideas for making your own scenarios. Plus, if you want to get to some of the really fun scenarios seen around, you simply can not do without these pieces. That is, unless you are big into painting your own sets of pieces (which is a fun way to personalize your own set).
Negatives: It still seems a little expensive to me. I am simply not sure if the wooden pieces and extra tiles are worth this much, but . . .
Verdict: No question, this is a must-buy. Unless you plan on making all of your own equipment from scratch, you need these extra materials.