Pros

• Well-integrated with the rest of the car
• Integrated system is aesthetically pleasing
• Large, 7-inch color LCD display makes the map easy to read from either the driver or passenger seat
• Dashboard display shows navigation prompts right under the speedometer, reducing the need to look at the 7-inch console display
• GPS speed sensor connected to the airbag accelerometers, providing map tracking even when the GPS can't get satellite signal. This is especially handy when driving through long tunnels.
• NAVTEQ mapping data
• Navigation system integrated with the car's stereo speakers and hands-free speakerphone. The system even lowers music playback volume to announce a maneuver, then raises the volume back.
• Real-time traffic supported via XM Traffic subscription (requires annual subscription)
• Good routing engine
• GPS gives good amount of advance warning of a pending turn. For example, when driving on a highway, the GPS will announce the next maneuver at 3 miles, 1.5 miles, 1000 feet, and 250 feet.
  

Cons

• User interface is complicated and difficult to use
• Map screen missing key pieces of information (such as arrival time, distance to destination, street name, etc.)
• Erratic displaying of street names on the map. Sometimes you really want to see the street name, and the GPS just doesn't display the name, no matter what zoom level you choose.
• Map updates require costly DVD rom purchases
• LCD is not a touchscreen. All controls are operated via physical buttons.
• Altimeter only measures altitude in increments of 100 feet
• DVD-based storage can be slow when performing certain data-intensive tasks, such as searching the POI database
• Some street addresses cannot be entered (must use house number ranges instead of exact house number)
• GPS signal performance not as strong as SiRF's StarIII
• POI Search function cumbersome and confusing
• POI inaccuracies/omissions (the GPS didn't know where JFK airport was!)
• Software not as sophisticated as handheld GPS units
• No Bluetooth support
• No route optimization feature (ability to enter a group of addresses and have the GPS order the stops in the most efficient manner)
• No route exclusion feature (ability to avoid a particular road or highway)
• Text-to-speech voice sounds computer generated, stilted
• Cannot search for an address by zip code
• Relatively few configurable options
• No ability to enter custom POIs
• No ability to watch video on the 7-inch display (in the USA. Apparently the European version does allow this)

Conclusion

At first glance you might think German engineers left no stone unturned in designing the 2007 Mercedes-Benz SL55 AMG Roadster. Step on the gas and the 500+ horsepower V8 pins you to the seat as you barrel down the highway. Styling is elegant and beautifully executed.

Use the COMAND Mercedes Navigation System just once, however, and that illusion is quickly shattered. The system is overly complex, with menu options cryptically named, and the user interface is frequently counter-intuitive. In my testing, I found Mercedes' COMAND system inferior to even the most basic $300 stand-alone GPS unit. It's hard to deny the aesthetic benefit of having the GPS navigation system integrated nicely into the dashboard. There's no unsightly wires to deal with and you don't have to worry about someone stealing it. However, a frustratingly complex interface plagues this system and will quickly have you reaching for an after-market GPS. The COMAND system also lacks features commonly found in even basic stand-alone GPS units, such as route exclusion, the ability to search for an address by zip code, a touchscreen LCD display, and custom POIs.

The Mercedes COMAND Navigation System does get a few things right: the system is well integrated with the rest of the car, and the routing engine performs acceptably well. The dashboard displays the next maneuver right under the speedometer as well as on the 7-inch console display. The GPS automatically lowers the audio of music playback when a navigation prompt is announced, and then raises the volume again, and the GPS speed sensor is connected to the airbag accelerometers, providing map tracking even when the GPS can't acquire a satellite signal.

Given the ~$150,000 price tag of the SL55 AMG Roadster, you'd expect nothing short of perfection in every aspect of this luxury automobile. Instead, the COMAND navigation system is poorly designed and fails to deliver even the most basic feature set in an easy-to-use package. Using the system all but requires you to do some owner's manual reading. The COMAND software needs to be given the same attention to detail as the rest of this car. Hopefully Mercedes will overhaul its COMAND software in future models. Until then, you'll have a much better GPS experience buying a unit from one of the well known manufacturers, such as Garmin, Magellan, and TomTom.