 The new S550 is quite a change from the previous S500.  Much more luxurious, but faster, better road feel and better fuel economy.  Best car I have had.  Only time will tell about reliability.  Got mine with special seats, keyless and 19" wheels.  The I- drive does it right (intuitive like the Audi, not awkward like the BMW)  Intuitive (unlike the BMW) and easy.  Nav system is simple to use.  Voice activitated controls extensive and it learns your own voice.  Really works and is once, again easy.