The italia 458 has a 7 speed dual-clutch GETRAG with 6th and 7th being overdrive gears.
http://www.autoguide.com/new-cars/20...cpe/specs.html
If you drive an italia 458 someday, you will notice something very peculiar in that car which is its ability to keep pulling after gear changing in the same intensity. you don't feel any loss of power after a gear change and i believe that a boosted S54 with a V3si can achieve the same when the gear changes drop it from 8K to 6K RPM.
As you climb the power ladder in our beloved Z4M, you start to feel how the gear ratios are layed out for a civilized street friendly car, especially when most of the supercharger gains are in 2nd and 3rd gear, useless in 1st and very ordinary power gain in 4th and 5th. 6th is just the fuel saving idiot gear.