I am a dye-hard TGM fan!!!
Tourguide Mike's info is so great; it really made our trip last time. We didn't wait in any line longer than 15 mins...and that one time was for Dumbos. He has tons of pictures and tips on where to sit for all the rides/shows/parades, etc. More than last year. He has best AM and PM to go to each park and best rides/shows to see in each park broken down by AM, PM, Afternoon, any time, etc.
I'm using TGM for our trip this year, too, and have noticed that he is keeping everything updated very well...he even dates the pages when the info changes so you can tell if it's up to date.
WDW changes so often that by the time a guidebook hits the shelves, some of the info is outdated. Passporter is the most up to date guidebook out there because they wait to put out the 2004 edition in 2004...not late 2003 like the others. But I've already had to download Passporter updates for changes WDW has made since it went to press.
If you have any specific ques, I'll try and answer them.
I was skeptical of purchasing it the first time, but someone told me you're spending 1000s on a vacation, isn't it worth $20 (less now with discounts) to make sure it goes well...and they were right.