 I bought the Audi S5 last month.  I was torn between waiting for the supercharged V6, or getting the V8.  After all of my research, I discovered, that the V6 will be on average 2-3 miles per gallon more efficient.  Which if you drive 15,000 miles a year, and extrapolate over a 5 year car ownership averages to about $2000 saved for the V6.  I chose the V8 because I test drove both engines, and the V8 just sounds better, feels better, and I personally like feeling the gears change and shift, because it makes me feel that I am driving a rocket.  The car is beautiful, handles superbly, the interior is well- appointed, and looks great.  The MMI did require some learning, but I'm good with it now. 