I'd highly recommend TGM!
Even if you've been to WDW a few times before, he has "alot" of information on the site.
Yes it will take considerable time to navigate through it all, but you can put your trip together piece by piece, customized just for your groups likes and dislikes.
He knows of what he speaks, and he updates all the time, so unlike a guide book his info is current, and his tips are dependable.
He helped make our last trip much more memorable, as we were able to use many of his tips to save time, and see many more attractions than we would have on our own.
But if you do use TGM, use it in conjunction with all the other sources of info out there. That way you'll get a balanced perspective.
Happy planning!