I have Birnbaum's "Official Guide", Bob Sehlinger's "Unofficial Guide", Rita Aero's "Essential Guide", and the Fodor's WDW Guide. I'm kind of a vacation planning nut, in that I'll do whatever I can before the trip to avoid wasting ANY time on the trip.
My rankings are:
1. Sehlinger's Unofficial Guide. His book takes a methodical, thorough approach to WDW. I used his analysis to rank every attraction before going to WDW last year into three categories (Must See, Sounds Fun, Avoid). Among other pieces of information, he presents the Scariness Factors for each ride. This book is incredibly helpful in avoiding lines/wasted time.
2. Aero's Essential Guide. Of all of the guidebooks, this one has the best format. The indexing is excellent, the page layouts pleasing, and the maps outstanding. Good tips, as well.
3. Fodor's WDW Guide and Birnbaum's Official Guide. I find both of these books to be well below the standards set by the first two. These two are poorly formatted, loaded with spoilers, and lack the age-by-age ratings that the first two have.
I have not read the Passporter book, although I may have to now for comparison purposes ...