First of all its not very expensive. I gave mine 4 coats even though the reccomended is 2 or 3, and still had half a bottle left. So for me that works out at €40 a season, I'd spend that on carwashes and cleaning products alone if I didn't use this stuff. Not to mind all the wasted time spent scrubbing the hull.
I think there's a little more to it than just being Carnauba wax. You do not polish it like a normal wax instead leaving it to dry. First it will dry to a haze and then you think the obvious thing to do is polish it, but if you leave it dry longer, it goes clear, so its not like your conventional wax.
I coated the bits of my tubes that touch the water as well, with no discolouration or any adverse effect.
Have had the boat on a mooring in dirty green water for nearly 2 weeks. Plan to leave her there for at least another 2. So far from looking at her planing in another RIB, there is no growth. The only sign of any marking, staining was the water mark on the transom (which is supposed to happen as there is no friction in this area to wash the marking off). Anyway, I just wiped the transom with my fingers and it was spotless.
I'll let you know more after a few weeks. There's a money back guarantee as well so it won't hurt to try it, just be sure to read the instructions or it won't work. It'll give your hull a nice shine and should improve your speed/ consumption (I cannot comment on this as I put the wax on before the boat was launched and so have nothing to compare to). After hearing what others in my locality have said about it though, it does work and some have gained 1-2 kts using it.
If In Doubt, Go Flat Out!!