I am putting the water wetter in my SC430, since the coolant is Toyota and already red so the weird gunk I am hearing about will likely not be visible in the coolant overflow tank.
I have some hyperlube which is like the water wetter but its green, and will use that in my 98 Mark VIII LSC. These products do work, and I know mechanics and people that like to race and they swear by it. The highest drops in temp will be if you use less or no coolant at all and only water. I have seen on many forums where people put these products into their cars, and its been the difference between running hot, and running normal.