Came across this article which talks about a potential performance gain of 8%, but by the looks of it not worth the hassle! (good read though)
http://forum.sailingscuttlebutt.com/DISCUSSION_C6/Dock_Talk_F5/Hull_coatings_P8414/

I think it could be useful to treat the tramp and snufferbag, also because it has UV protection built in.
Might even be useful to spray the inside of the hulls with as well