I'm quite pleased with them.
The boat will plane at lower speed and lower revs, (1 up about half throttle with the 3hp!) The boat remains level, and will plane at a lower speed. (I can plane and just about keep within the speed limit on the river 6mph
They didn't improve top end speed, I get 10mph with the 3hp. I haven't tried the 9.9 without the lifters. But can get 25mph, perhaps a bit more with less weight in the boat)
They'll perform diffently on other boats, but have increased planing weight and reduce fuel consumption.