I've only had my M5 for a month but in that time I have come to appreciate the beauty of this car. Sport car performance in a four door sedan. Engine that sings a beautiful song and has performance to match. Handling almost as good as my S2000 but without the harshness. Interior amenities to match any other manufacturer. The only downside is the poor gas mileage, but that is not the reason I bought this car.
Engine, seating and comfort in general.
SMG transmission still needs some work on programming. I am happy with iDrive after reading the manual and using it for a while.