The Good: The powerful engine, responsive steering, and adjustable suspension of the 2008 Mercedes-Benz CLK550 give it a sporting character. The Driver Multicontour Seat option lets you fine-tune seat comfort. The Bad: The interface for the cabin electronics is unintuitive and not aesthetically pleasing. The cartridge six-disc changer makes loading CDs difficult and ID3 tags for MP3 tracks aren't displayed on the car's LCD. The phone system relies on a cradle rather than the more accessible Bluetooth technology. The Bottom Line: The 2008 Mercedes-Benz CLK550 Cabriolet, while very enjoyable to drive, suffers from older cabin electronics. It has more than enough power and good performance characteristics, but for this kind of money, we would get something more up-to-date. Photo gallery:2008 Mercedes-Benz CLK550 CabrioletThe vast model lineup from Mercedes-Benz ensures that one of its cars will suit just about anyone's needs, but the 2008 Mercedes-Benz CLK550 Cabriolet fits a very narrow niche. The CLK550 is a coupe, offered as a convertible or hardtop. With the convertible version, which we reviewed, trunk room is so limited that a couple would need to use the back seats for luggage during a weekend getaway. Four people can fit in relative comfort, but forget bringing anything else. The car is fast and handles well, but its bland looks won't appeal to most sport drivers. It would make a very comfortable commute car, but the weekly gas bill would be on the high side. Its cabin electronics are all a generation old, with such quirks as a glovebox-mounted cartridge-style six-CD changer. At least it didn't have a cassette deck, as we recently saw on the Acura TL Type-S. We're not fans of the tech interface, which uses a washed-out blue color scheme and a fiddly joystick, and hope that this model will soon be updated with the interface we saw in the less expensive Mercedes-Benz C300. But the bland exterior and the poor tech interface aside, the CLK550 has a very comfortable cabin and can be an exciting car to drive. Test the tech: Navigation versus local knowledge Navigation systems determine routes based on what the digital-map makers mark as the best roads to get through an area, usually giving priority to freeways and highways. We tested the navigation system in the CLK550 by choosing a couple of destinations around San Francisco, setting the route guidance, and seeing how far off it wanted to go from our local knowledge of the best way to get through the city. For our first test, we set a course from CNET headquarters, in the downtown area, to the Golden Gate Bridge. Luckily, it was a sunny and reasonably warm day, so we put the top down. Even if a car doesn't look like much from the outside, a convertible top makes everyone else around envious, and ups the driving fun, even if you are just cruising. We reached the Golden Gate Bridge after only four arguments with the navigation system.Our first argument with the navigation system came when it wanted us to turn off Howard Street and go up Third, which would have taken us through the congested heart of downtown San Francisco. We ignored that direction, and the navigation system quietly recalculated the route. The CLK550 easily jockeyed around the light traffic on Howard, and its big 5.5-liter engine let us leave the slowpokes behind. Although the navigation system wanted us to continue down Howard, we took a right on Seventh Street, which would become McAllister Street in a few blocks, taking us through the city's Civic Center. While the navigation system would have avoided this area, we had always found that traffic moved reasonable fast. The navigation system advised us to take a right onto Van Ness, but that would have been suicide. We understood its reasoning--Van Ness is also Highway 101. But we locals know that the one-way Franklin Street, paralleling Van Ness one block over, is the faster way to go. Even as we ignored the Van Ness turn, heading to Franklin, the navigation system wanted us to go past our preferred route, but we took the turn onto Franklin anyway. Once it recalculated based on our current route, we had no more disagreements all the way to the bridge. Our total for this run was four arguments with the navigation system. We took a subsequent run from the San Francisco Zoo, way out on the southwestern corner of the city, back to CNET headquarters. For that run, we agreed with the navigation system for most of the trip, until it suggested we take Market Street all the way through downtown, a tedious route that would have taken us just short of forever. Instead, we chose to hop down 11th Street into the faster-moving South of Market area. For this run, we only had two disagreements with the navigation system. In the cabin One of the pleasures of driving the CLK550 on our various road tests was the sheer comfort of the cabin. The black leather, plastics, and wood trim all blended in together smoothly while the white face over the instrument cluster gave the car a performance look. The power top goes up and down fairly quickly at the push of a button on the center console. And our tester came with the Driver Multicontour Seat, which uses air chambers in the seat bolsters and back to let you dial in the perfect seat shape. Of course, sunny days and a convertible helped our enjoyment of the car immensely. We truly hope this is the last of these Mercedes-Benz interfaces we will see.On the downside, the 2008 CLK550 uses the same electronics that Mercedes-Benz is starting to phase out, the cheaper version of its COMAND system. The car comes with a difficult and ugly interface for navigation and audio that you control through a push-button\/joystick and soft buttons along the sides of the bezel. The function of these soft buttons changes depending on which application you are using, and it's often difficult to determine if you should be pushing a button or using the joystick. The navigation option itself offers basic functionality but not the advanced features we are starting to see in other cars. If you are not zoomed in all the way on the map, it generally doesn't show street names, which can be annoying, and when it does, the letters often have jaggy edges, making diagonal names difficult to read. But route guidance is accurate, and the LCD graphics get supplemented by a display in the center of the speedometer, which shows basic guidance directions. The points-of-interest database includes the usual run of travel-related places, such as restaurants and gas stations. One feature we like is called Today's Plan, which lets you add multiple destinations, then click a button to find the most optimal route to each place. It can even compute the route as a round-trip. Moving the sweet spot around the cabin makes for a dramatic change, but using the joystick to do it can be annoying. The stereo is another example of older tech. Our car had the six-disc changer option, which meant a glove-box-mounted cartridge player. At least it wasn't in the trunk. Both the six-disc changer and the single-CD slot behind the LCD play MP3 CDs, but the display can only show file names, not full ID3 tagging information. Sirius satellite radio is also an option, and Mercedes-Benz mounted an auxiliary audio input inside the glove box. An iPod integration kit is available, but wasn't present on our tester. The audio system is by Harmon\/Kardon, and it sounds good, but not fantastic. In the CLK550 Cabriolet, this audio system only has six speakers--centerfill, subwoofer, and four door woofers--which seems to limit audio qualities such as separation. Although we like that you can move the audio sweet spot anywhere around the cabin, the fact that you have to use the little joystick to do it means it will never be exactly centered. We like the information display in the speedo, but would prefer a modern wireless Bluetooth hands-free cell phone system.As with the last generation of Mercedes-Benz cabin electronics, this one relies on a cell phone cradle system for hands-free calling. The dock for the cradle sits at the back end of the console, and will continue to look ugly and go unused in most of these cars. As we saw with the C300, Mercedes-Benz has embraced Bluetooth for its future cabin gear, so it might be worthwhile to wait for an upgrade to the CLK550 if you are interested in buying. Under the hood Much like we've seen the cabin electronics in previous Mercedes-Benz models, we've used this engine in other models we've reviewed. The CLK550 gets the 5.5-liter V-8 we first saw in the S550 last year. In the CLK550, its 382 horsepower pushes it to 60 mph in 5.2 seconds, according to Mercedes-Benz. We can believe that. In our driving, this engine had plenty of power on tap--whether we were on the freeway, going uphill, or driving backroads, we never lacked power. But that power comes at a price. The CLK550 gets an EPA-rated 15 mpg city and 21 mpg highway, subjecting it to the $1,000 gas guzzler tax. During our driving, we observed an average of 18.7 mpg, not great mileage but not much below what we've seen in V-6 sedans. Although emissions ratings for the 2008 Mercedes-Benz CLK550 Cabriolet hadn't been published at the time of this review, the 2007 Mercedes-Benz CLK550 Coupe got a ULEV II rating, one better than the minimum. The steering in the CLK550 is responsive but light, offering very little feedback to the driver.During our time with the CLK550 we took it on a cruise from San Francisco to Concord, about 30 miles east. Instead of taking the boring freeway, we went up through the Oakland hills on various roads with names such as Wildcat and Grizzly Bear appended to Canyon and Valley. For the most part, these roads let us negotiate long, sweeping curves and straight-aways where we could let the car run. The suspension in the CLK550 can go from Comfort to Sport mode at the push of a button. We kept it in Sport, where it went noticeably rigid, limiting body roll while cornering. The steering wheel turned without effort as we dove into each turn--the steering is a little light for our tastes, offering minimal feedback about the road. But the big tires gripped without effort, and the big power plant made it easy to pull through a turn or pass slower vehicles on the straightaways of this two-lane road. Along with the 5.5-liter V-8 comes Mercedes-Benz's seven-speed automatic transmission, manually shiftable with a side-to-side motion on the stick or using the paddle shifters mounted to the wheel. We didn't find the manual shift experience terribly responsive--there was always a noticeable lag between the time we made the shift and felt it, which limits some of this car's sporting potential. In sum The convertible version of the 2008 Mercedes-Benz CLK550 comes in at a base price of $62,900. Among our options were the $2,290 navigation system and the $3,720 Premium 3 Package, which included the Driver Multicontour Seat, the Harmon\/Kardon audio system, and the six-disc changer. Along with its $775 destination charge and $1,000 gas guzzler tax, the total price came out to $73,035. We enjoyed driving the CLK550 quite a bit. It has lots of power on tap and the steering is responsive. And who doesn't like cruising around in a convertible? But the cabin gadgets aren't exactly cutting-edge, and we find the cartridge-style six-disc changer particularly laughable. The bodywork on the car isn't particularly striking, either, even with the AMG wheels and styling we had on our tester. For less money, you could be in a BMW 335i hard top convertible, which has better cabin electronics. But the CLK550 has the more comfortable interior.