The S430 isn't as lavishly equipped as the S500, but it's hardly spartan. The S430 comes with premium leather on the seats, seat backs, side panels, head restraints, magazine pockets, and door trim inserts. The seats are firm and multi-adjustable. We were surprised our S-Class car didn't come with seat heaters, and it turns out they are optional on the S430 ($650), standard on the S500.

The S500 adds premium leather to the remainder of the seats, center armrest, and door. The S500 gets glove-soft Nappa leather seating surfaces in place of the premium leather, and it doesn't get much lusher. The S600 gets the glove-soft Nappa leather in the other areas.

The rear bench seat feels like an expensive sofa. There's a cavernous 40.3 inches of legroom back there, just one inch less than the front. The rear seat reclines, too, if you check off that option. Four-place seating is available, providing rear occupants with bucket seats. Active ventilation is also available for the rear seats.

Mercedes says the design goal was to reduce driving stress as much as technology and good design sense would allow. Watch out for the ambush by an oxymoron, however: Technology and good design sense often fight for control, and, at least initially stress is sometimes increased rather than decreased. The instrument panel includes about six dozen switches and controls, some labeled with baffling icons, as if the translation from German to sign language had somehow come out Greek. Press a switch, just for fun. "Airmatic Vehicle Car Rising," a message on the panel tells you. Press another one and you've just turned off the Parktronic system, good to know when you're backing toward that big pickup expecting the system to warn you when you're getting close.

The car comes with its own video training course. The glovebox is crammed with operating manuals in black leather packets, including a separate one for the standard COMAND (COckpit MANagement and Data) system. This includes the GPS navigation and Tele Aid, which is basically a cellular help line for specific problem situations. In its latest incarnation, Tele Aid even includes traffic reports and concierge services. Then there's the optional InfoServices, which provides web-based customized information including news, stock quotes, sports and weather.

Reduce driving stress? The sheer mass of the manuals is stress-inducing. It's daunting to think about all the controls you have to learn to master so you can feel like a master of the universe. And even if you fully understand them, it would take so much attention to keep all the auxiliary systems perfectly tuned, all the potential for information fully optimized, that a co-pilot would be very helpful. Maybe that's where the voice command feature comes in. Some stuff you can just tell the car what to do, and hope it understands you. After you learn its language.

Ergonomics-wise, the center console has great support for your right knee, bracing your throttle foot. But there's nothing on the left, no real dead pedal, and not enough seat support for your thighs, so your legs get pitched during aggressive cornering. We know, the S500 is a luxury car, not a sports car, but if you offer a suspension that boasts level cornering, the driver should be expected to use it.

The S430 we drove featured a substantial cupholder sprouting out of the left side of the passenger seat. It works well, but it rubs against the passenger's left leg and we couldn't figure out how to remove or stow it. Speaking of stowing things, there aren't enough places to stow things in the S-Class. "People have stuff!" complained one passenger. Also, drivers who are not familiar with driving a Mercedes may find themselves turning on the cruise control when they meant to signal a turn.

The roofline, the C-pillar, creates a blind spot when you look over your right shoulder. But there's no blind spot through the windshield, not even in the spray of a truck in the rain, thanks to powerful wipers with no less than six nozzles to spew washer fluid.

Naturally, the Bose sound system is state of the art. More things that can be optimized, more features programmed for individual tastes. Soundstage positioning, it's called. According to Mercedes, "From a driver in the car alone, listening to talk radio, to a car full of people, listening to symphonic or vocal music, there is an audio setting to make the listening experience more enjoyable." But the quality of the rock 'n' roll we listened to didn't knock our socks off. Maybe we didn't have our soundstage positioned perfectly. Don't they have engineers for that, at concerts?

Like all navigation systems, there is a learning curve to mastering the NAVI system and you can expect frustration and distraction levels to increase until you reach that point. We found ourselves fighting off the audio when we wanted to operate the navigation system. And we could not figure out how to select a house number after entering it. The NAVI system in our 2003 S430 also seemed slow at calculating routes.