Mostly unchanged for 2010, the stylish Maserati Quattroporte continues to offer luxury sedan buyers a refreshing (though expensive) alternative to the ubiquitous Mercedes-Benz S-Class and BMW 7 Series. Since its introduction in 2005, the Quattroporte has seen continuous improvement aimed at meeting the lofty demands of American consumers.

Last year’s facelift made the already stunning Quattroporte more aggressive and sporty looking than ever. Its flowing contours are unmistakably Italian, and its low, aggressive stance reminds us of Maserati’s history as a racecar builder. Though most are wowed by the Quattroporte’s sultry shape, some find that the design is growing a bit long in the tooth in what is now the fifth year of production.

Three Quattroporte trims are offered for 2010. The Quattroporte 4.2 stays truest to the luxury formula with its powerful yet balanced V8 engine and (relatively) pothole-friendly 18-inch wheels. Quattroporte S trims benefit from a larger, 4.7-liter engine and big dual-cast brakes housed within 19-inch alloys. The hot-rod Quattroporte GTS is lowered and features a stiffer suspension that improves the car’s already stellar handling, plus less-restrictive exhaust tuning so enthusiast drivers can really hear the engine sing.

Under its beautifully formed skin, the Quattroporte features a traditional unitized rear-wheel-drive chassis. Constructed of steel, yet weighing in at a relatively svelte 4,200 pounds, the 2010 Quattroporte feels taut and ready to pounce. The almost perfectly balanced 47/53 weight distribution contributes to the Quattroporte’s incredible handling prowess, enabling this big sedan to run circles around the competition. The downside of this responsiveness is a rather edgy, unsettled ride and a lack of directional stability on the highway.

Few engines can match the exquisite sound and power delivery of the Quattroporte’s two V8s. Though the forced-induction units from Mercedes and BMW develop far more power, Maserati’s 32-valve wonder feels much more special, owing to its high-revving nature and Ferrari genes. In fact, the Quattroporte’s engines share their basic design with the V8 from Ferrari’s incredible F430 sports car.

The base Quattroporte’s 4.2-liter V8 makes a healthy 400 hp and 333 lb-ft of torque, while the punched-out 4.7-liter motor in the Quattroporte S and Quattroporte GTS serves up 425 hp and 360 lb-ft of twist. Both engines are mated to a slick-shifting ZF 6-speed automatic transmission. The much-maligned DuoSelect automated manual gearbox has been discontinued.

Stepping inside, the Quattroporte offers cabin accommodations that rival those of cars costing far more. Nearly every surface is clad in rich Poltrana Frau leather, hand-selected and stitched the old-fashioned way. This supple, fragrant leather makes the machine-stitched hides from Mercedes and BMW feel like vinyl, though the lack of synthetic finishing renders it far more susceptible to wear and tear. An endless variety of interior hues are offered, and owners can select from different wood trims, including exotic African Tanganyika, or go with carbon fiber for a sportier look.

The interior ergonomics and switchgear are modern but retain just enough of that charming Italian quirkiness. The new Bose stereo and navigation system, developed at great expense, sounds exceptional, but suffers from poor button layout and overly complex menus. Air conditioning flow has been improved, but the system still feels weak on hot summer days. Though not as spacious as the limousine-like S-Class, the 2010 Quattroporte’s power-adjustable rear seats allow for maximum space efficiency.

To be sure, the 2010 Maserati Quattroporte isn’t for everyone. Its six-figure pricetag certainly places it out of reach for many. Buyers who can afford it should note that the Quattroporte doesn’t respond well to neglect or harsh treatment. Though service isn’t the nightmare it once was (remember the Biturbo? Maserati hopes you don’t), owners should be ready to adopt a laconic, carefree attitude toward nagging little issues and costly maintenance bills. Those who do will be rewarded with an automobile that makes every commute or errand feel just a little more special.