 S5 is indeed a beautiful car.  I just got it, but I must say it is not that great of a car.  I own an M5 2007 so there is a big difference in performance.  When driving you must step on the gas more due to the quattro system.  When you release you will feel a slight deceleration which makes people think you are braking but you are not.  The handling is not as nice due to the really light wheel.  I do not get any feedback like when I drive rear wheel cars.  You will notice it the most when you drive on twisty roads.  I do understeer on turns since the line of entry is a little different with this car.  Great car for everyday drive but for performance the 335i can boogie against this car.  