The new Mercedes SL is a sinuous, sensuous roadster with dramatic styling. Press a button and, 16 seconds later, its retractable power steel roof changes it from the open-air fun of a convertible to the quiet comfort of a luxury coupe. The SL is packed with every bit of automotive technology that Mercedes has perfected over the past dozen years, and that's a lot of technology. It does everything well, assuming you like to travel light because there's not much luggage space.