The 2007 SLK 350 Roadster sells slowly in comparison with its Mercedes-Benz siblings. That's understandable. It's expensive and frightfully impractical. It accommodates two people, but not much of their stuff. Long-distance drives in this little car will leave you and your passenger stiff and grumpy. If you started out as spouses, best friends or lovers, there's a good chance you might not remain that way by the end of your journey in the roadster.

But on a beautiful spring day when nature and love are in bloom, the SLK 350 is a motorized aphrodisiac. It's stunningly attractive, especially with the convertible hardtop down. It's fast. It's sexy.

Slip a Sergio Mendes disc into the CD player. Push back the electronic lever that controls the hardtop. Crank the volume . . . modestly. Find a curvy road.

Alone, or with company, the SLK 350 is a marvelous car to drive as long as you don't ask it to do what it was not designed to do comfortably -- take you round-trip 300 miles in one day. The power-adjustable seats are the main problem.

There isn't much space inside the SLK 350's cabin. That means if you are accustomed to leaning back a bit as you caress the steering wheel, forget it. The driver's seat, for example, keeps your body upright, whether you want to be upright or not. (I felt like I was back in seventh grade at Holy Redeemer Elementary School in New Orleans facing Sister Vincent, her little round spanking rod and her stern admonitions to "Sit up, Warren!") I could take that punishment for 50 miles or so in the SLK 350. In fact, on short trips, being in this rear-wheel-drive runner does not feel like punishment at all. It's downright fun! The six-speed manual shifter fits nicely in hand. The shift throws are short, precise -- absolutely no hunting or fumbling around for the right gear. The car is wonderfully responsive to the driver's directions.

But much of that driving glory fades when reality intrudes, such as getting stuck in traffic jams on narrow roads in Fairfax County. Your shift arm gets tired of shifting. Sitting upright becomes a day with Sister Vincent: "Straighten up! Lift that head! Both hands on your desk!

"Stop that fidgeting!"

In the SLK 350, I was trying, but I could not comply. I wanted to get out. I was so happy when I turned into my driveway in Arlington I vowed never to leave it again -- at least not in the SLK 350.

My assistant, Ria Manglapus, had a different experience. She's short. She's small. The cramped, but elegant SLK 350 cabin and its sit-up-straight driver's seat did not bother her. "This is a fun car," she said. "I love it!"

Of course, she did. She's a mother of two boys. She's accustomed to carting them, their many cousins, their many friends and all of their stuff around in her 2003 Honda Odyssey minivan.

By comparison, the delightfully selfish, you've-earned-this, you-deserve-this SLK 350 was a dream. It made Ria feel so good, she scheduled a haircut during the two days she had the car. But reality cut short her roadster fun, too. "Gotta take the boys to school, and this won't work," she said upon returning the SLK 350.

And maybe that's the point: It's not supposed to do taxi work. The SLK 350 is a toy, an escape from hauling the world's daily cares. It is the essence of luxury -- splendidly extravagant, totally unnecessary and good for nothing much except bringing a smile to your face as you round a curve or take a corner in complete confidence.

That it lacks long-trip comfort is a plebeian complaint, the kind of bah-humbug mumbled by people like me, who often can afford only one vehicle to handle all transportation duties -- hauling five or more passengers and their stuff comfortably on trips of all durations.

To the SLK 350, that is base work. The car's sole existence for being is to provide intense moments of sheer driving pleasure. That's "moments," not hours or long days. The patricians who can afford the SLK 350 understand that. If they must travel 300 miles or so, they'd hire a limousine, or hop the first-class coach of a train or jet.

And so, for all of you to whom such class distinctions are important, here is how you can tell a driver who can afford the SLK 350 versus the one who has borrowed it, or is struggling to make the car payments: The poseur drives the SLK 350 everywhere all the time, treating it like a commuter, which it really isn't.

Nuts & Bolts 2007 Mercedes-Benz SLK 350

Complaints: It's expensive, impractical and designed to stay that way.

Ride, acceleration and handling: Acceleration and handling are top-notch. The electronic stability-control system in the SLK 350 is one of the best available -- constantly monitoring steering inputs and quickly acting to correct errors, such as turning too quickly into a curve. Ride is excellent for trips of 50 miles or so on relatively clear roads. But with its cramped cabin and up-righteous seats, trips of longer durations, especially in heavy traffic, can become a chore.

Head-turning quotient: Deliberately hot, sexy, sporty. It turns heads everywhere.

Body style/layout: The SLK 350 is a front-engine, rear-wheel-drive luxury roadster with a power-operated, convertible hardtop roof. It has two side doors, two seats, no cabin space for cargo and a teeny trunk that can handle two small overnight bags. SLK models include the tested 350, the base 280 and the top-of-the-line SLK 55 AMG.

Engine/transmission: Standard equipment includes a 3.5-liter, 24-valve, V-6 engine that develops 268 horsepower at 6,000 revolutions per minute and 258 foot-pounds of torque at 2,400 rpm. The engine is linked to a six-speed manual transmission. A seven-speed automatic transmission that also can be shifted manually is optional . . . for $1,430.

Capacities: There are two seats. Cargo capacity is 9.8 cubic feet. The fuel tank holds 18.5 gallons of required premium unleaded gasoline.

Mileage: We had a city/highway mileage of 20 miles per gallon.

Safety: Antilock brakes, electronic stability and traction control, and side air bags are standard.

Price: Base price on the 2007 Mercedes-Benz SLK 350 Roadster with manual transmission is $47,400. Dealer's invoice price on that model is $44,082. Price as tested is $57,620, including $9,445 in options (key fob that can operate doors, convertible hardtop and windows; premium audio system; Mercedes-Benz Tele Aid emergency communications system; onboard navigation; Sirius Satellite Radio, among many other spiffs) and a $775 destination charge. Dealer's price as tested is $53,640. Prices sourced from Mercedes-Benz and

Purse-strings note: It's a great toy. Compare with BMW Z4, Nissan 350Z, Porsche Boxster.