I agree with Wheel on the improved access without the booster. Plus for me, I could never get the feel of braking with the booster, all of my previous autocrossing and track days had been in a manual brake car. First time I hit the brakes on the AS, I almost went off the track.
Having the booster gone has made doing a leak down check a 20 minute process instead of 1 hour, changing plugs, and even making sure those last two spark plug wires were on tight used to be a pain with the booster in the way. Now, super easy, you won't know how much better it is if you never fought with the booster.