From the FAQ and other things I'm reading - it would look to be an interesting experiment for classes that are frequently pulled out of the water. I'm thinking it might be worth a test for the Lasers, Finns, etc to see if this hydophobic stuff is advantageous. Durability seems to be questionable amongst most the reviews of hydrophobic sprays on the market (UltraEverDry is not the only one).
This video shows how the stuff keeps a thin film of "air" between it and the water, which implies the friction coefficient of the surface (at least in water) is going to be vastly reduced.
On the other hand, the stuff is VERY expensive and quite toxic. Like quite a few anti-foul recipes, I'm betting if this proves advantageous - the environmental agency of some countries are going to start looking to see how bad it affects their marine environment.