Jaguar coupes have never been known for swift evolutionary changes. The XK8 was in production for 10 years, the XK-E made it to 13 and the XJS survived to the ripe old age of 21. In human years, that would be like living to see your 225th birthday. However, with the brand first on the brink of being flushed down the corporate drain and now under ambitious new Indian ownership, Jaguar can no longer afford to let its halo car rest on its laurels for years on end. That's why the 2010 Jaguar XK boasts major changes for both coupe and convertible versions.

One significant complaint we've had regarding the XK in the past couple of years has been the lackluster 300-horsepower output from the base V8. For 2010, the XK features an all-new 5.0-liter direct-injected V8. With 385 hp, it's putting out 15 more hp than the heavier BMW 650i and 3 more than the much heavier Mercedes SL550. The supercharged Jaguar XKR never drew any criticisms for its 410-hp V8, but we welcome with open arms this year's supercharged 5.0-liter mill with its upgrade to 510 horses. Given the fact that it has 10 more horses and 80 more pound-feet of torque than a BMW M6, the new XKR should be one wild kick in the teeth.

But there's more than just a power boost for 2010. Jaguar Drive Control, a new feature this year, offers the driver a choice of three different modes to alter the car's sporting responses via attributes such as throttle response, shift speed and suspension settings. The adjustable suspension with adaptive dampers is also new, and it's been designed to maximize ride comfort and handling prowess depending on driving conditions. An electronically controlled limited-slip rear differential is another new feature this year. Design-wise, there are slight adjustments to the exterior to bring a more aggressive and coherent look to the Jag's fascias, while the interior features a welcome supply of improved materials. Finally, the 2010 XK receives the XF sedan's trick rotary gear selection knob, which elegantly rises out of the center console upon ignition.

Overall, Jaguar has really upped its game with the 2010 XK coupe and convertible. The power boost, additional standard equipment and more elegant-looking interior have made the XK fully competitive against already impressive players like the BMW 650i and M6, Mercedes-Benz SL550 and SL63 AMG, and Porsche's 911. It's also worth noting that the XK is less expensive than its principal competitors. The 2010 Jaguar XK has already evolved far beyond its original iteration -- let's hope Jag doesn't let it rest on its laurels for the next 17 years.

The 2010 Jaguar XK is available in coupe and convertible body styles, with each offered in XK and XKR trim levels. Standard equipment on the base car includes 19-inch alloy wheels, bi-xenon headlights, front and rear parking sensors, keyless ignition/entry, leather upholstery, power-adjustable front seats, a heated power tilt-and-telescoping steering wheel, heated and cooled front seats and automatic dual-zone climate control. Also standard are a touchscreen control interface, Bluetooth, a navigation system and a Bowers & Wilkins premium surround-sound system with in-dash six-CD changer, satellite radio and USB audio interface. The convertible features a power-retractable soft top and power rear windows.

Options include adaptive headlights, adaptive cruise control and HD radio. These items are standard on the XKR, as are a supercharged engine, different 19-inch wheels, bigger brakes, and unique interior and exterior trim. Optional on both the XK and XKR are 20-inch wheels and different interior veneers.

The regular XK is powered by a new 5.0-liter V8 that produces 385 hp and 380 lb-ft of torque. The 2010 Jaguar XKR features a supercharged version of the same engine that pumps out 510 hp and 461 lb-ft of torque. Power is sent to the rear wheels through a six-speed automatic transmission with manual shift control. EPA estimates for the base coupe are 16 mpg city and 24 mpg highway and 16/22 for the base convertible. Both XKR body styles are just slightly less at 15/22 mpg.

Standard safety equipment includes antilock disc brakes with brake assist, stability and traction control, and front-seat side airbags. The convertible has pop-up rollover hoops.

Sent through corners, both the standard 2010 Jaguar XK and the XKR display the advantages of aluminum construction, as both versions of the car feel more agile than their predecessors. The new automatically adjustable suspension constantly maximizes ride comfort or handling, depending on the situation. Still, with its suspension biased toward a plush ride, the XK isn't as responsive on a twisty road as a Porsche 911. If you want something that will comfortably eat up hundreds of highway miles while occasionally venturing onto a scenic back road, though, the XK is ideal.

We haven't had a chance to drive an XK with its new engines, but since one of our former beefs with the XK involved its lackluster base power plant, this year's infusion of 85 hp should be a fruitful addition. There were no such objections to last year's 420-hp XKR, so the new 510-hp V8 should further the R's appeal.

The 2010 XK's interior is a pretty dramatic departure from the traditional Jaguar look, with a modern dashboard design and the availability of aluminum trim in place of wood. This serves to bring Jaguar into the 21st century, though some might argue that a Jag without wood is like Tom Selleck without the mustache.

For 2010, Jaguar has upgraded the cabin with higher-quality materials, specifically more surfaces covered in contrast-stitched leather. Also new is Jaguar's unique rotary shifter and "Handshake" start-up: The console-mounted start/stop button pulses red when the car is unlocked and, once pressed, fires the engine to life and raises the round shifter into the driver's hand. Some may find it gimmicky, but others will think it's incredibly cool. The multipurpose touchscreen that controls audio, climate, navigation and phone systems is also pretty cool and simple in concept, but we've found it frustrating in practice, with slow processing times and a non-sensitive screen. The abundance of standard features it operates, however, is certainly welcome.

As in any Jaguar, comfort is a priority. The front seats adjust in too many ways to list and feature heating and cooling. The power tilt--and-telescoping wheel is also heated, which is especially handy in the convertible for those cool autumn drives after you lower the power soft top (which takes a scant 18 seconds). The backseat, however, is suitable only for small children or emergency use, and even then, it had better be a major catastrophe. It's better than the 911's backseat, but that's pretty faint praise. The XK coupe's trunk can hold about 11 cubic feet of cargo. With the top down, the XK convertible can still hold a respectable 8 cubic feet.