It's the best money you'll spend on your trip!
DH and I just got back and were floored at other people telling their children things like, "Don't worry, we won't wait more than 45 minutes for things today." Signs were posted with wait times of 120 minutes and saw gobs of unhappy families waiting in those lines. We smiled at each other because we've never waited more than 15 minutes even for the best rides, and that was in holiday season. Those poor children; I bet they just wanted to swim in their hotel pool instead!
TGM is the very best, provided you understand a couple of things. First of all, you will have to do lots of research. So, if you are leaving on a trip in the very near future, it will not help you as much as if you sign up months in advance. Second, you have to put your plans together; he does not do that for you.
The forum over there is full of helpful folks who are absolute pros. They will guide anyone through any questions, whether they be about the site or an itenerary. I've been TGMing it for a few years now, and I've still never "seen" a fight. It's a really fun and disney-esque wasy to prepare for your trip!
Seriously, we would never go without Mike in the parks ever again. To think that we called our previous trips "vacations" when they weren't vacations at all! Mike helps make magical family memories, and he does it right!