The Hydrovane has been rock solid. It got us through our first major storm coming out of St. John's with flying colors!I have heard good things about the Hydrovane and the Cape Horn. The only one I have personal experience with is the Monitor and it was very finicky and had a bad habit of either loosing course or having the rudder kick up. Someone always needed to be in position to take over, so it was not very restful.
I had one of the early servo-pendulum models on a boat back in the '80's that was quite good but the hydrovane is stellar. This past day we have been running straight down wind, which can be hard on wind vanes, and the performance is excellent.
dj