I've used it combined with a little seafoam for about 3-4 years now. In that time I've noticed nothing - which is a good thing.
The tank of gas that I have in my 74 at the moment does not have either (seafoam/starbrite) in it as I was on a little road trip.
At work late last week, I noticed an odd almost crusty/ooze from around the float bowls.
It hasn't been there before (I'm pretty anal about my carbs) Carbs are one of the things I look at everytime I ride.
Don't know if I attribute the oozing to bad fuel or a lack of the seafoam/starbrite cocktail.
I like it at will continue to run it.