i live in the city so sport is my normal, on the highway im usually always sport plus...rarely in comfort mode.

also someone above mentioned using sport when getting on and off highways, most guys probably know this but if youre driving in PDK auto mode you can press the rear gear shift button on the wheel and it will downshift you for 8sec for a quick burst of speed. i do that alot if overtaking or getting on/off the highway...after 8 sec it reverts back to whatever gear you were in