This is my second S4 (I had a 2001 previously), and my 5th Audi. The design is great, interior elegant and ergonomic, and it performs great. But the reliability has been miserable. I only kept it for 6 months - it was in the shop every month of those 6 months. It went through brake rotors, had a coolant leak, an transmission cooler leak, the ABS system failed intermittently, and the check engine light came on (bad O2 sensors) twice. Probably the last Audi I'll ever buy - sad really.
Design, interior fit & finish, handling & acceleration.