I picked up the Official and Unofficial Guides for 2006 on Sunday.
I flipped through the Official one and will be returning it. I'm not one to normally return books, but it is just really the 2005 book with info on MYW tickets. I didn't read the book, just compared some pages, so I don't feel bad returning it. I was very disappointed, as I've bought this book every year for the past 6 years, and just can't justify the cost of keeping it this year.
Now, I love what they've done with the Unofficial Guide. The blue print somehow makes it so much easier to read. I have two friends at work who will be going to WDW in the next several months, and I've already shown them a few pages of it and told them they need to go to B&N and pick up a copy. One friend won his trip, so I looked up the hotel for him and showed him how it even listed drive times to get to each park. He couldn't believe the amount of detail and said he would have to get one. He hasn't been to WDW in over 20 years. He went to Disneyland this summer and while there won the trip to WDW. (He wins everything he enters. I've told him we need to take a trip across our state border to either VA, TN or SC to play the lottery and then both of us can retire!)
So my opinion is that if you have to choose between the Official or Unofficial Guide, choose the Unofficial. I did keep the Birnbaum Kids Guide, as my son is working on his reading skills and this guide gets him interested in reading.