It seems like the rumors of a four-door Porsche car have been dribbling out of Stuttgart for almost as long as MotorWeek‘s been on the air. Certainly, over the last three years, we’ve been fixated on every hint about the first sedan to wear the Porsche name in the firm’s 78-year history. Well, Porsche’s new flagship is no longer a rumor. This is the Panamera fastback sedan. Longer than a Cayenne SUV, it’s also the biggest Porsche ever.  So, can any car this large perform like a true Porsche? Well, now’s our time to find out.

The 2010 Porsche Panamera takes its name from the legendary Carrera Panamericana race of the 1950s.  While Porsche calls its first Gran Turismo a 4-door sedan, it actually has a rear hatch that makes five. But that’s only part of why Panamera’s styling is polarizing. While unmistakably Porsche, it’s on the conservative side, which should fit well-heeled sedan buyers. Frankly it also reminds us of a C6 Corvette-at the headlights, hood bulge, and even the side scoops.

With its long 115-inch wheelbase, and 195.6-inch overall length, the profile does start off coupe-like. But it becomes more tear drop towards the rear to allow for adult-sized backseat leg and headroom, something the rival Mercedes-Benz CLS lacks. The back view is wide, as if through a fish-eye lens. The hatch is well concealed, as is the retractable spoiler, with uniquely styled quad exhausts. Wheels are 18-inch standard, with optional 19’s.

The Panamera is also the first front-engine Porsche car since the 928, driven by a pair of direct-injected V8s from the Cayenne.  Panamera S and 4S use the normally-aspirated 4.8-liter with 400 horsepower and 369 pound-feet of torque. The Panamera Turbo adds twin turbochargers for 500 horses and a massive 516 pound-feet of torque.

Gear change is Porsche’s latest 7-speed dual-clutch PDK automatic with manual paddle-shift mode.  It feeds either the rear wheels of the Panamera S or all four wheels of the 4S and Turbo models. At our track, our Panamera 4S blazed from 0 to 60 in 4.9 seconds, and shot through the quarter mile in 13.5 seconds at 105 miles per hour.  With Launch Control on, our car leapt out of the hole with a beastly roar. The PDK gearbox isn’t as quick as in the 911, but it’s smoother.

The Panamera’s chassis is defined by a front double-wishbone and a rear multi-link setup, all governed by Porsche’s Active Suspension Management. The adjustable dampers can be set to Normal, Sport, and suspension-lowering Sport Plus. In Sport Plus, we sliced through the cones in a razor-sharp manner. Steering response is perfect. The Panamera is a big, 4100-pound car. But that size seems to disappear the harder you push it. Our 4S also benefitted from optional Porsche Dynamic Chassis Control with its two active roll bars. Even at ridiculous speeds, cornering is flat.

Superb stopping power comes from four-wheel vented discs armed with six-piston calipers up front and four-piston in the rear.  Stops averaged a very short 116 feet from 60 to zero. The Panamera just squats to a stop.

While the Panamera’s exterior may be controversial, the interior is a feast for the eyes. Beautifully trimmed in wood and even carbon fiber, there’s plenty of space for its four adult-wide seats. Your focus is drawn to two areas: the cascading 5-bezel gauge cluster, and a center console master control panel.  There’s a lot of switches here, but they’re logically grouped. Navigation data is viewed on a large center stacked screen, and inside one of the gauges. Optional is a 17-speaker, 1000-watt Burmester stereo.

Rear vision is mostly blind spots, so both the available camera and front-rear parking sensors are recommended. The rear seats require little contortion to get to, and as we mentioned before, adults will find a generous space with headroom boosted further by a scalloped headliner. Amenities include adjustable vents, armrest with cup holders, and an available twin screen DVD system. Impressively practical, drop the 40/20/40 rear seats to expand luggage space from 15.7 cubic feet to a crossover-like 44.6.

Government Fuel Economy ratings for the 4S are 16 City/24 Highway on premium gas. We managed only 16.7 in mixed driving. The Panamera uses a mild hybrid-like start/stop system to shut down the engine at traffic lights.

Panamera pricing starts at $90,750 for the S, $94,750 for the 4S, and $133,550 for the Turbo. There’s no gas guzzler tax. That’s a notch above an S-Class, but comparable to an Audi S8. Naysayers can have a seat, because Porsche has done it.  The 2010 Panamera is a primo luxury sedan and sports-car-for-four all rolled into one.  Styling aside, this unique saloon delivers everything it promises, plus a lot more.