First, I'd like to express my sympathy for whatever embossed little creatures Jaguar uses to upholster the upper deck of this car, the Jaguar XJ Supersport. It's a dappled, caramel-and-coffee kind of skin, perhaps a jungle cat, perhaps crocodile, though it hardly matters since whatever it is will soon be rooming with the dodo. Indeed, the interior of this car is a glorious charnel house of animal hides, from the semi-aniline leather seats with the contrasting piping to the roof lining, door panniers, rear console and, of course, the steering wheel, which feels so exquisite I'm sure its wrapped in something awful, fetal kitten or somesuch. The Jag illustrates a maxim of luxury that comes down to us from the Romans: When in doubt, add cruelty.  Leather, and lots of it, is the signature interior flourish of the Supersport, the all-in, mega-performance version of the XJ sedan. The car is also fitted with some rather extravagant laser-cut wood inlays in the doors in a choice of six veneers; aluminum thresholds in which the word "Jaguar" glows in ice-blue; and a long list of other luxury fitments that confirm to the world you have no control once you sit down with the dealership's sales manager. In the previous regime at Jaguar this car would have probably been called Vanden Plas.  But none of these fineries should obscure the fact that this is a truly powerful, damn-near wild car, with a 510-horsepower supercharged 5.0-liter V8 under the hood (40 more hp than the Supercharged model), gristly suspension, huge brakes and ferocious 20-inch cat claws in the wheel wells. These tires go by a ridiculous name—Dunlop SP SportMaxx GT (275/35ZR20 in the rear)—but they are very seriously engineered bits and indispensable to the gestalt of the car, which is: balanced; direct; trustworthy; lightweight but with wonderful, gathering momentum; hugely stiff but with a certain useful limberness. More than once I gripped the wheel in anger and felt the leather-wrapped hilt of a very good broadsword, an eidetic race memory.  The Jaguar XJ Supersport thus hits a sweet spot between galling luxury and serious performance. Think of it as a car that drinks Champagne and then eats the glass.  I admit I've been a little bit in the bag for the new XJ since it came out. It just looks spectacular and a half-year later I'm more convinced than ever that a) it's the most beautiful mass-market luxury sedan, and b) it's not quite the technical equal of the comparable BMWs, Mercedeses and Audis. Now that I've spent more quality time in the car, there are things I would change: I think the graphics in the thin-film-transistor instrument display need to be refined and recast in higher resolution; the rear-view camera takes precious seconds to engage when the car is put into Reverse, and the system can hang up once you put the car in Drive, so that you may have to wait for the Navi screen to engage if you're not sure which way to turn. The mirror-chrome ashtray and release button in the console picks up fingerprints like a CSI unit. Some of the felt-like molded liner in the trunk of my test car had become detached in a way that was less about build quality than faulty design. And I don't think the yellow paper cones in the Bowers & Wilkins loudspeakers—declaratively visible through the perforated speaker cover—look very premium, less Pebble Beach than Pep Boys.  So in some of the details, not perfect.  Also, the car I drove—a regular-wheelbase XJ Supersport ($111,075)—does not enjoy the weapons-grade visual impact of the long-wheelbase model (5 inches longer), the easy grace of the roofline, the menacingly long and low stance. And, not surprisingly, the rear seat is not nearly as spacious and comfortable in the short wheelbase model. With the driver's seat where I like it, I was actually a little cramped sitting behind. Jaguar figures the short wheelbase car will be more popular in Europe where, in some cities, the bigger car would look a little ridiculous. The long-wheelbase model will be more popular in the States, the Middle East and China.  Personally, it's no contest. I'll take the longer car, with a weight penalty of a mere 49 pounds. But the company's design chief, Ian Callum, says he prefers the short-wheelbase cars because, he notes, as the car gets shorter, the wheels get closer and look bigger and badder. Interesting.  Powertrain: Supercharged direct-injection 5.0-liter DOHC, 32-valve V8; six-speed automatic with manual shift mode; rear-wheel drive with electronic active differential  Horsepower/torque: 510 hp at 6,500 rpm/451 pound-feet at 5,000-6,500 rpm  EPA fuel economy: 15/21 mpg, city/highway  Cargo capacity: 18.3 cubic feet  Not that these wheels need any help getting noticed. The Dunlops are wrapped around gorgeous 20-inch gunmetal-gray "Mataiva" alloy wheels with red center caps and, to save you a trip to Wikipedia, Mataiva is a tiny atoll in French Polynesia. (If I were marketing a 510-hp carbon hog like the Jag, I think I'd steer clear of references to Polynesia.)  The thing to remember about this Jag—or indeed any six-figure high-performance sedan, where cost is no longer a constraining factor—is that the way it drives is almost purely a matter of volition, which is to say, a matter of the designers' and engineers' choice. So yes, the steering feel in this car is surprisingly light and leveraged, even over-assisted, especially as compared with a car like the Porsche Panamera, which can feel like cranking on a steamship's boiler valve. But that liquid feel of the steering is the way Jag product design likes it and it really does remind me of some of the older Jags, like the 1990s-era XKs. It's a brand verity.  Likewise, the XJ Supersport shuns nailed-down, progressive power delivery—as you'll find in a BMW—for something that's a little more ornery, a little more vivid. In Sport mode, the throttle is as touchy as a South American dictator. Banging up and down the six forward gears with the paddle shifters, you can make the car jump and shout, overwhelm the active differential control and pitch sideways, where it's caught barely by the stability control. The nature of this car lies very much in its software. When you hit the rev limiter, the computers don't gently feather the throttle; they cut the gas to the engine with a garden hoe. When you light up the rear wheels around a corner and the traction control engages, it's a choppy, disapproving yank. Stomp the throttle and the dark, indignant sound is what you might expect if you punched a sumo wrestler in the kidney. Make no mistake. You're definitely driving something.  And so, volition. Jaguar wants this car to feel edgy and racy and a little bit stark. Refinement? Have you tried a Lexus?
Wrapping the driver in a nearly galling level of luxury, Jaguar's highest-performance sedan also delivers a stark, racy driving experience, says Dan Neil.