To be honest, this is the first time I have investigated him. I am going again in December so I can't report how useful the information I found is going to be. My feeling is though that so far it appears to be very detailed and I like that. I can tell you that on this site if you do a search you will find both good and bad reviews of him. I feel I have nothing to lose for trying it. There was nothing I have read here that screamed "stay away" so I will keep going with it.
So far, from what I have read, the information looks very good. There is a lot of great information about how to plan a trip, resorts, transportation, dining, etc. The best feature in my opinion is the section that details what parks to go to on what specific day. On Tour Guide Mike (TGM) he goes as far as to break it down into morning and evening. He gives more detail than The Unofficial Guide (UG).
In terms of the acutual tourning plans themselves, I have used the UG tour plan before with great success. I have looked over TGM's tour guide plan and my personal preference at this time is to use the UG plan. I am using TGM for all of the other information on the site as there is quite a bit and I like the level of detail in it that sometimes the UG lacks but I will definitely use the UG tour plan when I hit the parks. Make sense?
I am going at the busiest time of the year so don't want to take any chances. The UG website also has tailor made plans according to the ages of your kids. That is quite helpful. I will admit, that on the first time around, there were things that I could have done without seeing, but really that is part of the investigative process. The UG outlines everything worth seeing and from there it is personal preference. This time around, I am just deleting things that we didn't feel we needed to see again. TGM's plans are a bit more flexible for this type of thing, but I personally feel that the UG is a better plan for first timers who don't really have an idea about what all the attractions are and what they like.
Also, TGM provides up to date info regarding your travel dates. That is handy. TGM's site is loaded with information and some find it hard to navigate. I haven't had any problems as I go through step by step and print out the info to look at when I can. Being that you have awhile to go before the trip, you should have time to take full advatage of TGM. If you go int there knowing there is a lot and have a systematic way of breaking it down then you will be good to go.
Personally, I think you can get all the info you need from TGM and the UG sites. Disboards is also fantastic for checking out things you have read.
Hope this helps!