I used their engine flush, and fuel cleaners and conditioners in a 92 model triton I had. I couldn't believe how much "extra" oil came out with the flush. The fuel cleaners I wouldn't say there was power gains but starting was much quicker and smoother.
I tried the same products in the nav but didn't really notice any gains. Maybe the engine was just in better condition than the triton. I put the fuel cleaner through as well but i didn't have much left so I don't think it had enough of a chance to make a difference.
Been thinking about getting some more myself actually.