I just booked today for May 2011, and had no problem with availabilty. Ment to call at the 11 month out day but forgot. Was a little worried, but no problem.
What did concern me was they told me you can only park one car at the tree house! How are 8 people suppose to use one car. They said we could park the other car at SSR which is about a half a mile walk.
I may be rethinking my stay here.