Think of it as an "e- book" - if you usually buy a book on Disney, this is an electronic book - it has that much info - and that can be overwhelming! But like others said it gives you an idea of why you want to do things, so if our DD has an episode, i'm off track, but I know how to tour due to the info... If you dont read and spend time on the site, you can still get lots of helpful info in the forums - and my favorite are downloads, my dd is 11, and we printed stuff for her to read in lines that was useful, fun ( about the attractions... )
TGM also has a list of "best days" to go that are very useful,(maybe less crowded on a particular day) and again, I found my self having to go to a different park, but it turned out great, again, based on the advice of how to tour... imho