To quote Marchaj in aero and hydrodynamics of sailing - page 342
"In general conclusion it appears that the roughness of foils surface is always harmful, and the labour expended on perfecting the finish on the forward third of the chord of a rudder or fin keel is never likely to be wasted."
before this he comments that polishing the leading edge is a good thing but that you can pretty much do as you please with the rear third of the chord and it makes not much difference. He compares a highly polished surface with a surface sprayed with 180 carbundurum.
so thats bethwaite and marchaj and a guy from lockheed martin.... versus some comments from internet forum posters..........