I went through the Hummer Academy in August of 05, it was the best time I every had.
They teach you a lot of good technical aspects to 4 wheeling. And they do have some very neet trails, and you do spend a lot of time on the trails. All of the Instructors at the Academy are Great and you do get to bond with them while you are there.
I did have a lot of Off Road Experience before I went to the Academy, and I did learn a lot of good things at the academy and I did learn how to do things right when 4 wheeling. At the Academy they teach you a lot about your Hummer and how to become one with your truck. ( Just my way of puting it )
The cost for the Academy is High, and you do get a lot of cool stuff while you are there, and they do treat you like a king while you are there.
I spoke with one guy that has been thrugh the Academy 4 times and he does race off road for a living. I my self have been thinking about going back through the Academy again, I will say it is worth it.
When you leave you feel in total control of what you can do with your Hummer.