I personally don't know how good it is relative to the other supplements available because I've never used it but I can't magine that it is that much better. They simply have spent a lot of money to promote their product through the UFC and the fighters use it as part of the arrrangement between Xyience and the UFC.
As for whether all future UFC champs will use it, I am sure that if Xyience has their way it will be mandatory - and I'm sure their marketing contract with the UFC specifically addresses this issue.