Slick 50 gearbox treatment in 1.0L

I have just changed my my engine oil and added slick 50 gearbox treatment and I am stunned by the improvement!

The gear whine coming from the helical gears is far quieter and the gearchange nicer too. I found the additive for peanuts and bought it as I rembered the effect it had on a Ford Pinto engine years ago. For those too young to remember, it was one of the most rattly cantankerous engines ever. It was in the days of black sludge and was made of cast iron! The treatment in the engine that time was profound in its effect and I was curious as to effect this time. I know we have high air pressure at the moment, which tends to make engines run quietly, but I was still surprised.

I am not sure if I would pay list price, but the dude proved that some additives to have some good effects which this one certainly does. What have others found?