Just upgraded from 350 cab to the 550 cab. The engine on the 550 is amazing. Too bad the rest of the car lags in comparison. The suspension is downright sloppy. Straight line acceleration is exhilirating, but the smile on your face quickly fades if you have to turn, as it is plagued by execissive body roll and lack of control in corners. Stereo is so-so, and seating, even with the p-3 option pdg which includes upgraded "body contour" seats, is still far below the support and comfort of a BMW. If the BMW 335 convertible were available, I would have bought it. But it is not so I will enjoy this car for my 3 yr lease term and then trade for the more comfortable and sure-footed BMW.
Exterior looks. This is a fine looking auto, better looking than any of its competitors. Engine performance is amazing.
Better stereo. Better seats (AMG seats from SL should be made available--most comfortable seats on the mkt) Faster- shifting paddle shifters. Sportier suspension setting--this alone would transform the car markedly-the ABC system of the SL would make this into a world-beater.