I have used star tron in my Valkyrie and now the Concours, It does work well and you can notice it more with the carbureted engines. It does help with some of the break down of the fuel, I would say it does not work 100% but enough to were I had to only clean one carb not 6.
I put about 1 cap full at every fill up in the Concours just as an insurance blancket. Seems to be worth the $13.00 a bottle to me.