Most cars get redesigned every five to six years, which makes the 2012 Mercedes-Benz SL-Class all the more impressive. This old soldier is entering its 10th year since its last complete redesign, and even though it has been updated over the years with new engines, updated gizmos and an aggressive new face, the SL still retains the seamless blend of luxury and performance this retractable hardtop convertible has had since the very beginning. To be trite, it's an oldie but a goodie.

However, the current SL's life is coming to a close and several of its sub-models have already been put out to pasture. The SL600 and SL63 Black Series disappeared last year, and the twin-turbo V12 SL65 AMG has been discontinued for 2012. That's an awful lot of automotive fun resigned to the big used car lot in the sky, but any grief should be mitigated by the fact that the SL550 and SL63 AMG are still very appealing cars.

Either version of the SL can serve as a smooth-riding boulevard cruiser and capable back-road stormer, walking the fine line between comfort and performance in a way that Mercedes does so well. The SL's retractable hardtop roof is also available with a glass skylight, something that sets this car apart in a market segment that includes nothing but soft tops. Of course, when the competition includes such cars as the Aston Martin V8 Vantage, Audi R8, BMW 6 Series, Jaguar XK, Maserati GranTurismo and Porsche 911, it can certainly be hard to choose. Each is spectacular in its own right, yet also very different.

In a way, the fact that the 2012 Mercedes-Benz SL-Class is still relevant after 10 years is a testament to how truly excellent it is.

The 2012 Mercedes-Benz SL-Class is a two-seat convertible with a retractable hardtop that is available in SL550 and SL63 AMG trim styles.

The SL550 comes standard with 18-inch wheels, bi-xenon headlamps, a wind deflector, heated wiper and washer nozzles, automatic wipers, remote roof activation, a power trunk closer, keyless ignition/entry, auto-locking interior storage bins, dual-zone automatic climate control, eight-way power seats (with heating, ventilation, four-way lumbar adjustment, adjustable bolsters and memory functions), the AirScarf passenger-warming system, leather upholstery, a power tilt-and-telescoping steering wheel, auto-dimming rearview and driver-side mirrors, Bluetooth, a navigation system, real-time traffic, voice controls and a 10-speaker Harman Kardon surround-sound audio system with a six-CD/DVD changer, satellite radio, HD radio and an iPod/USB media interface. The SL Wheel package adds 19-inch AMG wheels, high-performance tires, upgraded brakes, shift paddles and dark-tinted head- and taillights.

The SL63 is a high-performance variant that features a more powerful engine, a high-performance transmission, different 19-inch AMG wheels and various AMG-tuned components (suspension, brakes, exhaust) and different styling. Inside you get AMG-specific styling flourishes, different leather upholstery and a sport steering wheel. The AMG Performance package adds a limited-slip differential, a more aggressively tuned suspension, forged alloy wheels, a beefier steering wheel and a higher top speed.

Both SL-Class models can be equipped with front and rear parking sensors, adaptive cruise control and a glass moonroof. There are also a number of "Designo" special-order options that bring special exterior and interior colors.

The 2012 Mercedes-Benz SL550 is powered by a 5.5-liter V8 that produces 382 horsepower and 391 pound-feet of torque. Rear-wheel drive and a seven-speed automatic transmission are standard. Mercedes estimates that it will go from zero to 60 mph in 5.3 seconds. EPA-estimated fuel economy stands at 14 mpg city/22 mpg highway and 17 mpg combined.

The Mercedes-Benz SL63 AMG gets a 6.2-liter V8 that produces 518 hp and 465 lb-ft of torque. It's all managed via a seven-speed automated manual transmission with shift paddles. In Edmunds performance testing, it went from zero to 60 in 4.6 seconds. Its estimated fuel economy is 12/19/14.

The 2012 Mercedes-Benz SL-Class comes standard with stability and traction control, antilock brakes with brake assist, side head/thorax airbags, a driver knee airbag and a pop-up rollbar that deploys automatically in the event of a rollover (it also can be raised by the driver at the touch of a button). Also standard is Mercedes mbrace emergency telematics service.

In Edmunds brake testing, the SL63 AMG came to a stop from 60 mph in a very short 108 feet.

How you experience driving a 2012 Mercedes-Benz SL-Class depends entirely on which model you choose. The SL550 is the boulevard cruiser of the two, yet we've found that the steering and Active Body Control systems produce a more satisfying performance car than ever before because the package is more in tune with the driver's intentions. And with 382 hp, you'll never be wanting for power, of course. This same endorsement also applies to the SL63 AMG, although to an even greater degree. It's a snarling beast of a machine, yet it still manages to be both comfortable and capable, showcasing a wider range of abilities than simply going fast in a straight line.

In the realm of two-seat roadsters, it doesn't get more spacious or more luxurious than the 2012 Mercedes-Benz SL-Class. With the hardtop raised, even our tallest editor (6-foot-3) had enough headroom, while legroom was also pretty good. The eight-way power seats offer a generous range of adjustment and feature a lengthy list of other features to keep you coddled and comfortable. These include heating, cooling, adjustable bolsters and the AirScarf system that gently blows warm air on your neck. There aren't too many cabins better suited to top-down motoring.

If there's one area where the SL shows its advanced age, this would be its older COMAND electronics interface, which features a central four-way toggle (not a knob). Newer Mercedes models incorporate a mouselike knob that's much easier to use.