Having owned a couple in my youth, I’ve had an admitted bias towards Jags my entire life. That said, I’ve had a couple of different opportunities to drive the 2003 Jaguar S-Type and the S-Type R, and honestly, have just fallen in love with this car.

The S-Type is as comfortable in the role of a 100-mph highway cruiser as it is hugging a winding two-lane mountain blacktop at nearly the same speed.

My first exposure was at a media preview of the revamped S-Type sedan line in Washington D.C. last year. I had the pleasure of a longer test period just recently. Besides offering superior performance, the latest S-Type also boasts more luxury, safety, and refinement — if that’s possible.

The undisputed champion of the show is the 155-mph, S-Type R. With a supercharged 400-horsepower version of the regular S-Type’s V8 under the hood, it does the 0-60 drill in a scant in 5.3 seconds.

“We want the R to put a really big smile on the faces of S-Type buyers,” Mike O’Driscoll, president of Jaguar’s North American Operations, told me afterwards as we cruised the Potomac on a relaxing dinner cruise aboard the presidential yacht, Sequoia after the test driving was done.

Jaguar introduced the R to compete with Mercedes and BMW who have brought out hot-rod versions of their regular models. There is also a bit of a precedent for such a vehicle since Jaguar already has a R-version of its XJ.

On the road, the S-Type offers an excellent package of steering, handling, and braking. But, except for the aggressive R, it seemed to me to be designed more for luxury than its rival European sports sedans — not that luxury is a bad thing. Although Jaguar modifies its vehicles slightly in all 70 world markets where it’s sold, a plusher version of the S-Type is sold in America than is in Europe, where it’s regarded as being sporty as opposed to luxurious.

Behind the wheel, the redesigned interior is cozy for sure, but has a more integrated look and feel. It features a new dashboard with a new full-width bird’s eye maple veneer panel and racing style instrumentation that can be read at a glance. The wood is gray-stained on the R-version, which also boasts a leather-wrapped steering wheel.

Although redesigned, the center console still occupies a fair amount of room up front. There’s an optional $2,200 DVD navigation system that in my view is a bit over-engineered. The climate and sound system controls are integrated into it and it can be pretty intimidating to the technophobe — and even a bit confusing to the tech savvy. Fortunately, the S-Type isn’t at all unpleasant to be lost in.

There are also comfortable new seats that define the specific characteristics of each trim level. The optional, electronically adjustable foot pedals are controlled by a small plastic switch on the steering column and can be programmed for two memory positions.

The S-Type offers a number of enhanced safety items, such as a new front energy absorbent seating system and new front and rear side-curtain airbags for head protection.

The trunk is long, but not particularly deep. The rear seatbacks do flip forward to enlarge the cargo area and allow easy storage of things like skis.

The S-Type has a sort of retro look that harks back to the Jags of the 60s — right down to the high window line that is suddenly stylish again, as witnessed by its use in the Audi TT and new Nissan Z-car. Although about 70 percent of the S-Type has new content, it still has that alluring styling of its predecessor.

There are a few visual changes like the revised grille and new outside mirrors. There’s also a special bright-finish mesh front grille that visually distinguishes the R-version from the other S-Types, and a rear spoiler to enhance high-speed stability. Special alloy wheels and the same red R logo used on the Jaguar R3 Formula One race car also separate it from the rest of the S-Type line.

Powerful xenon HID headlights with electronic headlight leveling round out the package. They’re standard on the R, optional on the other models.

But it’s under the hood where the business really takes place. The regular S-Type V8 has gained size and horses, going from 4.0 to 4.2 liters, and 281 to 300 horsepower. It moves the S-Type from 0 to 60 in 6.2 seconds, while providing better fuel economy and lower emissions.

The S-Type V6 remains a 240-horse 3.0-liter powerplant, but new 3-stage variable geometry induction and continuously Variable Cam Phasing move it from 0-60 in 7.3 seconds. Not too bad for the heavy, equipment-laden car expected to be purchased by about 35 percent of S-Type buyers.

The V6, which previously was offered only with an automatic transmission, can now be coupled with a new Getrag 5-speed stick. The V8 comes with a new 6-speed ZF automatic, which is optional on the V6.

I like the J-gate setup on the shifter of the automatic and got comfortable with it quite quickly. A mode switch near it gives the driver a choice between normal and sport shift modes.

There’s a new braking system with a four channel anti-lock setup and “panic assist” braking for emergency stops. There’s also electronic traction control and a standard Dynamic Stability Control. An improved Computer Active Technology Suspension is standard on the S-Type Sport and R versions.

Whines: The trunk lid has manual hinges that eat into cargo space that can ill afford it. The navigation system is disconcerting at best and a downtright unpleasent experience for the non-techie.

Applause: The R is the definitely the sexiest S-Type, but all the 2003 line has been improved enough to lure those considering rival cars — as well as current S-Type owners — back to the showroom. If the R is off the financial radar screen, Jaguar offers lower-priced Sport versions of the V6 and regular V8 models with a color-keyed exterior, leather sport interior and upgraded sport suspension and brakes.

Bottom Line: Ford-owned Jaguar has made lots of significant changes that drastically improve the S-Type for 2003. The R-version is far and away the star of this model line, but the others hold their own against the competition. It’s a little spendy, starting at $42,495 and climbing over $62,000 for a loaded S-Type R. But money aside, this is one hell of a great car.