I went for the first time this year. I had only been riding 1 1/2 seasons before.
I had in mind that I would learn a bunch of new tricks. Instead, they made me go back to the basics and change a bunch of bad habits that I had built-up. Then they made me do real basic stuff like ollies, ollie 180's, wake jumps, one wake 180s and so on.
At first that was a disappointment for me. Later at home, I realized that I was much more solid and that I was able to progress a lot quicker.
One piece of advise: Try to go at a time when you have not been wqithout riding for a long time (i.e. at the end of your season). I went in May, which means I didn't ride in 7 months. The first few days were spent just getting back "into it" and fighting muscle pain!