Here are my recent experiences:
It was, unfortunately, due to circumstances beyond my control as they say, over a year between my last slip footage of Zephyr. 18-06-2012 I was out last year until 26-06-2013 this year. So she has been in all winter. 446 running hours, she has gone over the period with an average speed of approximately 20 knots. Mostly cruising around 25-28 knots with peaks around 35 knots.
As shown on the attached photos, I have not any growth of barnacles and only a little green algae in the water line, the trim tab edges and drive. This green algae has not resulted in any increased fuel consumption during the period and dropped slightly at the end of the period.
The unit has been in operation for the entire period and I am becoming more and more convinced of the good it does.
Hope this information is helpful for your evaluation!