I've driven several of these cars and just bought one. They are extremely powerful and smooth driving. I also drove the Lexus SC400 and SC430, the Porsche Boxter and 911 and several others. They're all fun, but for my money the SL500 is tops. Driving with the convertible top down and the Bose stereo up is quite an experience. Try it!
The acceleration and handling.
More comfortable seats bottoms (might just be my particular car).