which is where you never let off the gas peddle and just puch the clutch in shift and pop it and go...I have noticed quite a bit of difference in acceleration. But I am still getting used to it. first to second is fine and third to fourt is fine but second to third and fourth to fifth still scare me...last night speed shifting from first to second i threw the back end out on my stock n/a it was hella squirlly my wheels were perfectly straight too, it was cool...i'm sure its bad for the clutch but nissan just put one in about 3k ago and screwed me on it so if I fry it before my 12k warranty i really dont give a shit :) anyways just my 2 sense speed shifting is better than double clutching cuz it faster i think...