I have nothing against mouse/keyboard use, or button clutch for that matter (I used it myself when I was using mouse, to do manual shifts). It's the button clutch script thingy that bugs me, giving you perfect and insanely fast shifts. And yes, I'm sure it can give a whole second advantage on the longer tracks. I've tested it myself, and on a short track I was 0.4 seconds faster with it than without.