You can see the wire in the picture running down the back of the shifter, it's held on with a narrow strip of double sided tape. No one notices it.
The GV gives you one fast shift on the strip, I use it going from second to second over, it probably does help the times.
I use the car on the street a lot and tend to dip the clutch when I switch the overdrive in because its very harsh if you don't. I don't use the clutch if I have my foot to the boards and the revs are up. A floor switch would make it difficult to dip the clutch.