Generally the efficacy of any anti-fouling is a function of location so my observation is predicated on New England - results may vary...
Having said that, used it the last two seasons. Prior to that, nothing was used and we found dozens of various sized critters on the prop even though we used the boat 3-4 times per week. In the last two years of using the Petit, the boat has sat idle for prolonged periods and upon hauling at the end of each of the past two seasons, there were only a few (3-5) small barnacles. That plus the fact there was visible paint remaining indicates to me this stuff really works.
I use interlux spray on for the 35hp on my dink. I have it on both the outdrive and the 4 blade prop. No idea what the prop spins at but the engine runs at 4-5K and I cruse at 16kn. It's harder than the ablative and shows no ware and so far nothing sticks to it here in the Pacific North West. I also no longer get any galvanic action on the prop. But then it's not in the water 100% of the time either.
I guess the best answer is would I use it again? Definately!