If you compare a lap where you couldn't get all the downshifts done properly with your mechanical shifter to a geartronics lap, you will find a significant difference. If you compare a mechanical shifter lap where you performed every shift without incident to a geartronics lap, you will have a hard time finding any time advantage. If you think otherwise, you will be dissapointed with your geartronics purchase. I put one on the car because too many laps got spoiled by inability to downshift. Whether that was because I couldn't build a reliable mechanism or my driver is a hamfisted gorilla, who knows, probably both. I just know you can't win a race if 5 or 20 times you can't get the right gear to accelerate out of a corner, so of course, it is an advantage having a geartronics.
If you are either a magician with your mechanical shifter, or yours works flawlessly, you just aren't suffering timewise. You may disagree, but regardless, I'm not being disingenuous. I can honestly say I would take the geartronics off if I had a mechanism that was much lighter and worked every time.