Big, fast in any of its variations, and exceptionally smooth. The solidity of a bank vault. Virtually every convenience imaginable, from massaging front seats to electric door-close assists, and the most sophisticated passenger-car safety technology money can buy. Yes, the Mercedes-Benz S-Class has everything the world expects in a full-size luxury sedan, including a stratospheric price tag. It remains the ultra-luxury car against which other ultra-luxury aspirants are judged. This is the flagship of the Mercedes line, and recognized as such in every corner of the globe. The S-Class is sleek and aerodynamic, right down to the polished Tri-Star hood ornament that symbolizes status from Beverly Hills to Boston to Berlin to Baghdad. Yet that gleaming star only hints at the engineering underneath. There's much technology here, and learning all of the features takes some time. The S-Class is smaller, lighter and more efficient than those built in the 1990s, yet inside it is roomier. Microprocessors and onboard sensors instantaneously determine forces acting upon the car, filter the data, then adjust the handling, engine or transmission performance. The safety systems can actually anticipate a collision, and prepare the driver and passengers to get through it as safely as possible. Electric seat belt tensioners are activated, and the power seats adjust to a lower and more upright position. Mercedes-Benz calls this Pre-Safe, and says it is the only system in production that engages before the impact, when milliseconds can minimize the energy spikes that cause serious injuries. The S-Class offers four engine choices and optional all-wheel drive. The S430, the most popular model, has plenty of power for quick passes, merging into fast freeway traffic or accelerating out of corners, and it exudes the presence buyers in this price range expect. The S500 delivers much more responsive performance, with crisp off-the-line acceleration that should please any closet hot-rodder. The V12 S600 represents the ultimate in Mercedes-Benz luxury and power, with thrust and acceleration that feels like a 747 approaching rotation speed. The S55 AMG is a limited-production high-performance model geared toward wealthy motorheads. A year ago the S-Class benefited from a mild face-lift that freshened its styling around the edges. There are more updates for 2004, starting with the first seven-speed automatic offered in a passenger car. A new DVD-based navigation system eliminates the need to change CDs for movement between regions. Other updates include MP3 capability for the stereo and optional 18-inch wheels for the S430 and S500. Is this the best ultra-luxury sedan available? The S-Class doesn't deliver the athletic feel of the new Audi A8L or the reflexes of the BMW 7 Series. Its control switches, all six dozen of them, can seem intimidating, and sport-minded enthusiast drivers can sometimes feel as if they're wrestling with all that electronic technology. Yet a certain arrogance of engineering has always been part of the Mercedes tradition, and a component of the brand's charm. Well-healed buyers seeking the classic big luxury sedan should start with the Mercedes S-Class.