The 2006 Lexus IS350 is the latest car to be defined by one of automotive journalism's favorite tropes: "The fill-in-the-blank is the car that's finally going to dethrone the BMW 3-series as the benchmark for contemporary sport sedans."

Although lots of American, European, and Japanese manufacturers have tried the Bimmer on for size, none has measured up. Lexus took a shot with its outgoing IS300-and missed the mark. Sold in Japan as a Toyota and badged in the States as a Lexus, the original IS was too small and too light on luxe to knock the 3-series off its pedestal.The new-from-the-ground-up IS is more powerful, more refined, more cleverly packaged, and more liberally equipped than the car it replaces. That's the good news. The bad news is that BMW can make the same claim for its freshly overhauled-and frankly Lexus-ized-3-series. The question now is whether Lexus can hit this fast-moving target.Lexus increases its odds of scoring a bull's-eye by offering three versions of the IS and a pair of all-new engines. The entry-level IS250 is powered by a 2.5-liter V-6 rated at 204 hp. The IS250 AWD adds all-wheel drive. The full-boat IS350 reverts to rear-wheel drive but gets a potent motivational tool in a 306-hp, 3.5-liter V-6 that bristles with technological wizardry.

All three cars ride on a tautened version of the platform that underpins the recently released GS430 high-end sport sedan (and the coming GS450h luxury hybrid). The cars also share the same basic independent suspension architecture: control arms at the front and a multilink arrangement at the rear, with coil springs and antiroll bars at both ends. The IS's tuning, though, is substantially livelier.

There's no mistaking the family resemblance between the IS and the GS. The IS is the second pro-duct of Lexus's "L-Finesse" school of exterior styling. The sheetmetal of the high-waisted car is pulled tightly around the stubby nose and billows out at the rear to give the IS some serious booty action. To our eyes, the execution is a bit sterile. But in profile, the IS looks an awful lot like-yep, you guessed it-the BMW 3-series.

The new IS is visibly larger than the old one-3.5 inches longer and 3.0 inches wider, with 29 percent more trunk capacity. (The dimensions are uncannily close to the BMW 330i's.) The difference between past and present is even more obvious inside the cabin. The rear seats, which had been a joke-a painful joke-now offer enough legroom for a pair of living, breathing adults. Tall drivers, too, will be a lot more comfortable, thanks to ample headroom and cocoonlike seats.

The quality of the materials as well as the fit and finish are up to the usual Lexus standard, which is to say beyond reproach. The lightsaber-look floating needles on the instrument gauges no longer elicit oohs and aahs, but they still do the job. The optional navigation system, meanwhile, offers an intuitive touch screen featuring a display that's better than that of many laptop computers.

Grab the beefy steering wheel of the IS350 and your fingers almost automatically curl around a pair of hard plastic shift paddles artfully crafted to look and feel like brushed aluminum. Alas, Lexus hasn't developed a sequential manual gearbox like BMW or Audi, nor does the slick-shifting six-speed automatic do the Infiniti blip-on-downshift thing. Then again, with 277 lb-ft of torque available at 4800 rpm, who cares?