We were just there for New Year's. I knew it was going to be crazy, and since this was our first trip this time of the year, I took advantage of the Tour Guide Mike discount at the top of the page and gave it a try. We didn't follow the plans exactly the first couple of days (fairly close though and still had very successful visits to DHS and AK), but followed them religiously on 1/2 and 1/3 at MK and Epcot and he was dead on with his advice. We breezed through the parks with extremely low waits, and even got to do some of our most popular choices multiple times. The time saved, and the fact we got to do everything we really wanted to do was well worth the money spent.
I have followed some of the "free" online sites recommendations before and was fairly successful. When we return for our July 4th trip, I will definitely be using Tour Guide Mike again, though. The best part to me is that everything is constantly updated as the conditions dictate, so you get the latest and best info right up until you leave, and if you have internet access when you arrive, you can still check for updates to see if you need to make any adjustments.