it can be overwhelming at first but there is a LOT of great info. Try starting with the "in a hurry?" planning section. It's a lot less info. By the time you plow through that you sort of have a feel for it and can find your way around much easier.
IMHO, it's the best planning tool out there! We've used it twice during busy times (week between Christmas and New Years and in April) and have not waited more than 10-15 minutes for anything, usually between 5 and 10. On our last trip we ran into some friends from home. Neither of us knew the other was going that week. Our experiences were VASTLY different; they went with minimal stratgey only from one or two guidebooks and we were using TGM. We ran into them in Fantasy Land just before lunch time. We had been there for EMH and had already done with everything in Fantasy Land (except IASW and Philharmagic), Buzz, DH and DS had done Splash, we'd done Pirates, Jungle Cruise and Haunted Mansion, and Tomorrowland Transit Auth. We were headed to get Fast Passes for Philharmagic thent o eat lunch, see Philharmagic ride IASW and back to the WL for a break. Our kids were happy and enthusiastic...we were all having a great time and had not waited more than 5 minutes for anything. They had been there for 2½ hours, had been on 2 rides and were searching for something with less than a half hour wait. The kids were fussy, the parents were fighting and no one was having a good time. It was like we were on 2 different trips!