I saw a couple guys doing the no belt thing at the track once. They would pull the belt off right before they staged and put it back on on the return road. I saw them do it several times and they swore it saved them a couple tenths, but it seems to me there are better ways to shave a couple tenths, ie electric fan, short belt, lose some weight etc.. I've always raced my car the same as I would on the street, with the possible exception of slicks (I run Drag Radials now). The guy in the Camaro SS next to me at a light ain't gonna wait for me to pop off my serpentine belt, and if I can't beat him with it I don't deserve to win.
Just my $.02