I used to fill up twice a week with premium until I decided I wanted to do a TT swap and stopped caring so much about the NA motor. I never noticed a difference in my mileage or performance, although I did note my hesitation dissappered, but that could have been the new injector connecters!
I say if it's your car and you want to take the chance and save some cash, go ahead. But at the same time one thing I will not do is beat on my NA with 87 in it. If I know I'm gonna have some fun, I go fill up on premium.