The Good: Tech and luxury fuse in the 2007 Mercedes-Benz S550 as in few other cars. Well-designed interior systems, a panoply of practical safety features, and impressive performance deliver a truly top-notch driving experience. The Bad: With options, the price of the 2007 Mercedes-Benz S550 can easily sail into six-figure territory. The COMAND main control interface is better than iDrive but still requires a day with the instruction manual to master. The Bottom Line: The 2007 S550 is a fitting flagship for Mercedes-Benz, offering cutting-edge technology to go with excellent performance for a full-size sedan. It's expensive with all the gizmos but trumps the competition in nearly every respect. Review summaryThe 2007 Mercedes-Benz S550 is an all-new luxury sedan presenting the best the iconic German car manufacturer has to offer. Like previous generations of the S-Class line, the S550 coddles driver and passengers alike in luxurious surroundings, while taking electronic control over interior systems and driving aids to a new level.The extensive list of technological features starts with an infrared night-vision-assist system, which neatly combines a high wow factor with real safety benefits. Distronic radar-based cruise control and brake assist also incorporate safety and convenience by automatically maintaining distance from vehicles up ahead. Features include full stops and starts in traffic (an option on the cruise-control stalk enables the car to resume speed from rest in tandem with traffic flow; no pedals needed), as well as preparation for heavy braking when cars in the S550's path are slowing rapidly.Front multicontour seats contain electronically adjustable air bladders and offer numerous massage settings in addition to heating and cooling controls and 14-way power positioning. The front seats also automatically adjust the side bolsters to grip the more zealous driver in heavy cornering.From the outside, the 2007 Mercedes-Benz S550 is slightly longer than its ancestors, with an extra 3 inches in the wheelbase. It also sports muscular wheel-arch bulges. Despite this nod to current car couture, the styling is still generally restrained, in keeping with the understated confidence the S-Class has long represented. Inside, soft leather and rich wood are complemented by indirect ambient lighting and quality switch gear.Our test car was loaded with options, such as active body control, a panorama sunroof, Sirius Satellite Radio, electronic trunk closure, power rear seats, and four-zone climate control, in addition to those already mentioned. The total retail price was a whopping $105,000, including $775 for destination and delivery and a $1,000 gas-guzzler tariff.The 2007 Mercedes-Benz S550 makes the kind of seductive first impression that only a real luxury vehicle can. The familiar Mercedes door-closing thud gives way to the soft whirring of electric door-closing motors (as on the previous-generation S-Class), and once inside, there's no doubt you're in the executive suite of the auto world. Interior materials are all high quality, and the breadth of electronic features is immediately apparent.Keyless Go, an $1,100 option, allows the driver to keep the key fob pocketed while entering, then fire up the Mercedes-Benz S550 with a touch of an engine start\/stop push button.The main instrument panel contains the tachometer, as well as fuel and temperature gauges on either side of an 8-inch LCD, which shows a convincingly high-resolution image of an analog speedometer. This virtual setup allows info from other vehicle systems to be overlaid on the speedometer image so that audio, Distronic, navigation, trip computing, and telephone functions are all visible on the speedometer display and controllable by buttons mounted on the steering wheel. A virtual analog speedometer is displayed on an LCD panel on the S550's main dash, allowing the driver to monitor speed along with navigation, audio, and telephone functions on one screen.The 2007 Mercedes-Benz S550's Distronic display features a two-car image indicating the distance to the car ahead, while shading the speedometer's (virtual) rim to show how far below the intended cruise speed the target car is moving.Most impressively, this screen also doubles as the forward night-vision-assist monitor, with a very crisp image of the road replacing the speedometer. The system uses two infrared projectors and an infrared camera to detect objects--and potential hazards--up to 500 feet ahead. When in night-vision mode, the speedometer is displayed horizontally across the bottom of the screen.A second LCD in the center of the dashboard serves as the COMAND display. This screen can rotate a few degrees to skew slightly toward the driver or the front passenger, the kind of nice-to-have detail not seen in lesser cars. With a 16:9 aspect ratio and the same crisp resolution as the speedometer screen, it displays menus and images to control most interior systems. We found the single-knob COMAND system more intuitive and pleasing to use than BMW's iDrive solution, which we've panned liberally in reviews of the 750Li and the 550i, but that gets less annoying each time we encounter it. COMAND makes effective use of various S550 diagrams to depict what the user is changing, especially handy when programming the endlessly adjustable front multicontour seats (an $1,800 option).COMAND extends to features such as the power rear sunshade, interior ambient lighting, and exterior lighting delays, but frequently used features such as the sunshade mostly offer their own dedicated controls. Climate control is operated via a row of center-console buttons up front and a small screen and button group in back, although true to its name, COMAND can allow or disallow separate rear-seat control.The audio setup features a six-CD in-dash changer playing through an impressive 14-speaker, 600-watt Harman Kardon Logic 7 surround-sound system. Sound is predictably full at all ranges, and you can fine-tune the system through COMAND. A PC Card slot below the CD aperture lets the system play MP3 files from other media, and a specialized iPod adapter will be available as a dealer option.Mercedes-Benz's GPS navigation system is standard on the S550 and includes its own 20GB hard drive. Along with the stereo and telephone systems, navigation is controllable by voice, as well as via COMAND or two five-way pads on the steering wheel. We found the nav system commendably quick and accurate, no doubt helped by the dedicated storage, but street names were displayed on only maximum map zoom. A manually or voice-activated satellite navigation system with 20GB of dedicated memory comes standard. The system understood our voice commands with no problem, and programming destinations using the COMAND knob worked just as effectively. While in full-screen map mode, the system also displays the scale, the compass heading, the current latitude and longitude, and the number of available satellites--in case we were curious. For the nitpicker, the one drawback on the 2007 Mercedes-Benz S550 is that telephone integration requires more than a simple Bluetooth pairing. Bluetooth is available in the S550 but only to read address-book info from a phone, a PDA, or a laptop, not to make calls. Cell phones must be placed in a model-specific cradle in the center armrest and, once in place, are fully accessible both directly and through a keypad hidden under the padded wrist rest. Phone integration requires a cradle specific to the model of phone, which sits in the center console. Calls can then be made from a full touch pad.Clustered around the COMAND knob are 10 switches for sundry technical tasks, including alternating between interior systems and switching from Comfort to Sport suspension mode and various radio controls. One button is left to be customized for a radio function of the driver's choosing.Power rear seats cost $1,120, and the panorama sunroof is a $1,000 option. Our car also had an intuitive rearview monitor system, which offers helpful distance and intended path markings, for $750. Rear side-window blinds are power operated from the driver's or rear seats for $700. Satellite radio prep is $500, four-zone climate control goes for $1,200, and the night-vision option is $1,150. The base price of the Mercedes-Benz 2007 S550 ($85,400) is actually slightly lower than that of its predecessor, but it's easy to see how a six-figure bottom line soon racks up.Mercedes calls its newest 5.5-liter V-8 a new-generation engine, convenient marketing jargon that abandons its long-defended single-cam, V-8 layout in favor of a dual overhead-cam unit. The result is a stout 382 horsepower at 6,000rpm, with the peak 391 pound-feet of torque available from 2,800rpm to 4,800rpm. These power figures are substantial increases over the outgoing S-Class V-8's numbers, yet emissions have also been reduced, with help from variable valve timing.The ninth-generation 2007 Mercedes Benz S550 delivers more power than its predecessor but with fewer emissions. On the 2007 Mercedes-Benz S550, power goes to the rear wheels through a seven-speed automatic transmission. Buttons on the back of the steering wheel allow manual shifting, but the broad power band and the number of available gear ratios mean that acceleration is brisk from any speed, and picking gears manually is redundant--more for play than performance. Mercedes-Benz's official 0-to-60mph time is 5.4 seconds, very quick for a 4,270-pound car.Our test car's single most expensive option was Active Body Control (ABC), at $3,900. It consists of hydraulic pistons at the top of each wheel's coil spring and is controlled by a computer monitoring 13 sensors: 4 in the wheels to gauge level and 9 around the body to detect movement. New data is read every 10 milliseconds, with suspension damping updating accordingly every 120 milliseconds. It was difficult for us to judge the system's real-world effects without having driven a non-ABC-equipped version, but as with the BMW 750Li's roll-bar twisting system, body roll is almost fully eliminated. Its contribution to ride comfort was very noticeable over rough San Francisco streets, where the S550 seemed to float over potholes. Speed-sensitive power-assisted steering melds well with ABC, never feeling overboosted and maintaining good feedback at all speeds--no mean feat in a car more than 17 feet long.The 2007 Mercedes-Benz S550 is EPA-rated at 16mpg in the city and 24mpg on the highway. According to our test car's trip computer, it had averaged 17.7mpg at an average speed of 29mph during its previous 1,613 miles. With the possible of exception of a few 6,000-pound leviathans on the current SUV market, the 2007 Mercedes-Benz S550 has to be considered the safest passenger car on the road. Most of the active safety features are available in similar guises in other cars, but the S550 integrates them in a unique manner.The rearview-monitor system is one of a range of technology features that convinced us to give this car top marks for safety.Compared with earlier heat-based systems, the S550's night-vision assist is much more effective at detecting objects up to 500 feet ahead and providing a clear picture with no washout from oncoming headlights. One of our favorite safety features was the Distronic system's radar sensors, which allow the 2007 Mercedes-Benz S550 to prepare for impending collisions in innovative and unprecedented ways. While seat-belt tensioning in preparation for impact is nothing new, the S550 can also move its seats to optimize air-bag effectiveness and adjust seat bolsters to hold occupants more tightly. (The current BMW M5 also features active seat bolsters for hard cornering, but they are not integrated with any collision-detection systems.) The front and full-length side curtain air bags therefore have an extra split second to deploy before a crash. The car's windows and sunroof are also closed if a possible impact is anticipated, reducing the risk of injury to those inside. If the radar detects that heavy braking is needed, it warns the driver while prepressurizing the brake system in anticipation of an emergency stop. ABS is standard, as has it been since the S-Class was the first production car to offer it in 1978.Other more familiar but no less-important safety offerings include a tire-pressure monitor, which displays each tire's reading on a speedometer-overlaid readout; a front-passenger occupancy sensor; the Tele Aid system to call for help in the event of theft, being locked out, or a collision; and electronic stability control.The warranty period for the 2007 Mercedes-Benz S550 is four years\/50,000 miles, including 24-hour roadside assistance.