Like everything else about the A4, the V6 engine is very smooth. Press down on the throttle and power comes on linearly, evenly. It does not paste you to the back of the seat, but delivers solid torque throughout the rev range. Variable-timing intake and exhaust camshafts optimize air/fuel delivery and combustion, boosting horsepower and presenting 90 percent of peak torque from 2200-5200 rpm. So there's a deep well of power available whether you're winding up on an empty country road or just cruising along. Jab the gas pedal, and the A4 responds immediately.

With the six-speed manual, the A4 3.0 is a match for BMW's 330i, long the performance benchmark in this class. The six-speed's gear ratios are nicely matched if you want to shift frequently and really work the engine. Yet the new V6 is flexible enough that you can shift less frequently, allowing the engine torque pull the car along. It's a nice gearbox, though not the easiest to coordinate with the clutch for smoothness. An A4 Quattro with the six-speed manual can accelerate from 0 to 60 mph in 6.9 seconds and can turn the standing quarter-mile in 15.2 seconds. That's comparable to a BMW 330i. The A4 is quick, the fastest A4 yet. Rarely will you fall into the passive mode at the wheel. More often than not you'll want to stretch it.

If you prefer an automatic transmission, you have two options: A4 quattros are available with a five-speed Tiptronic automatic. A4 FronTrak models offer Audi's Multitronic continuously variable transmission. Audi's CVT was designed to handle high torque loads, such as those from its 3.0 V6. It's lighter than conventional automatics, has fewer moving parts, and theoretically fewer things to go wrong. The practical advantage of a CVT? It provides the best transmission ratio for optimum performance or economy in any particular driving conditions. An A4 3.0 FronTrak with the CVT accelerates as quickly as an A4 3.0 quattro with the six-speed, according to Audi, and gets about the same mileage as an A4 with a manual transmission.

CVT takes some getting used to, however. Its clutch can take a second to engage, much like a torque converter that's slow to lock up. To the driver it can feel like sloppiness in the drivetrain. Depending on circumstances, you get rolling too slowly, or with a jerk, and working the throttle can require some practice. It's really a matter of getting used to different behavior. Audi has programmed its CVT with six pre-defined ranges, that act like gears. It can be managed by a Tiptronic sequential selector, so drivers can operate it like a conventional automatic with a sport shifter. We recommend driving the CVT before buying it.

The five-speed automatic Tiptronic transmission is a good choice for A4 3.0 models. Put it in Drive and leave it there. It offers responsive performance and communicates well with the 3.0-liter V6. Fuel economy for the A4 3.0 automatic nearly matches that of the A4 3.0 six-speed manual. Enthusiast drivers can slap the Tiptronic shifter to the right and shift manually. Pull the handle back to downshift, push it forward to upshift. The automatic does, of course, diminish acceleration performance when compared with either the CVT or manual gearbox (by 0.5 seconds in the quarter-mile, according to Audi). Still, the five-speed automatic with Tiptronic is a nice companion to the A4 3.0 quattro, and we thoroughly enjoyed it on our A4 3.0 Avant. It had plenty of punch. We never tapped the steering wheel impatiently, waiting for the acceleration to build. We were never anxious when we pulled out to pass. Around town it shifted very smoothly.

We are not sure we would enjoy the automatic as much with an A4 1.8T, however. We have not driven an A4 1.8T with an automatic, but have been less than pleased with the 1.8T/automatic combination on various Volkswagen models. The turbo and automatic do not seem to always work as a team. At low speeds around town, the turbo seems to confuse the transmission, resulting in reduced response then a surging sensation. We found this alternating behavior annoying. In stop-and-go L.A. traffic the automatic sometimes seemed surprised when we suddenly stood on the throttle when changing lanes, and the car hesitated before taking off, not good when other cars are barreling up behind. At higher speeds, however, the automatic shifted very smoothly and we wondered whether we were being overly critical. Also, 1.8T fuel economy suffers by 2 mpg around town with the automatic.

A4's steering is quick enough that a lane change requires only a small turn of the wheel, yet it isn't twitchy to the point where every slight movement on the steering wheel jerks the car left or right, requiring correction in the opposite direction. The A4 turns into corners with authority, but not abruptly. Rarely will you find yourself correcting your trajectory once you've committed to a curve. When driving an A4 Avant, you'll need to look in the rearview mirror to confirm you're at the wheel of a wagon. It's the only way to tell.

The A4's suspension features a sophisticated multi-link arrangement in the rear that replaces the old torsion beam axle found in pre-2002 A4s. This compact rear suspension makes room for a larger fuel tank. More important, it keeps the rear tires in better contact with the pavement, particularly on bumpy roads, and it delivers an even better balance of crisp handling and ride comfort. The optional Sport Package includes stiffer shocks, springs, and anti-roll bars, plus 17-inch wheels and P235/45YR17 ultra-high performance summer tires.

The A4's ride is firm, even without the sport suspension package; if you prefer soft and willowy, this may not be the car for you. We found the ride just about perfect: soft enough to soak up the bumps, never jarring, yet not so soft that the car seems to float over the surface with no feeling of control. Take a curve at a brisk clip and you'll feel firmly planted to the road, without the excessive lean that takes the fun out of driving some sedans.

Audi's quattro is a full-time all-wheel drive system that automatically shifts power to the tires with the best grip. If the front wheels are slipping, quattro delivers more engine power to the rear, more effectively turning that power into forward momentum. Quattro does more than improve traction on wet, slippery surfaces, however. It also improves handling in all conditions, because if one or two tires lose grip in a turn, the car is less likely to fully lose traction and slide. The all-wheel-drive system is coupled with an Electronic Stability Program (ESP), a computer-managed system that gently applies the brake at any one of the four wheels to help counter skids. All told, these systems make the A4 one of the most secure handling, confidence-inspiring small sedans in production.

We gave the brakes a good workout on the road up and down Vermont's Mount Equinox, where sports car clubs run organized hill climb competitions. This road is a series of tight hairpin turns connected by straightaways, and you'd better be able to count on your brakes. The A4 slows itself with authority, and we didn't experience a hint of brake fad after repeated full-on stops with little recovery time in between. That's reassuring. Further, Audi's ABS programming with Brake Assist senses panic-stop situations, and applies maximum braking even if the driver hasn't fully pressed the pedal.

At a more leisurely pace, nothing about the A4 stands out, with the possible exception of the V6, and that's good. Quattro, ESP, automatic brake proportioning are seamlessly integrated, and usually transparent to the driver. In short, the A4 is a well-balanced machine that will hold your interest, in the manner of a good marriage. It's exciting enough to grab your attention in the short term and substantial enough to grow more attractive with time.

The 1.8T with FrontTrak (front-wheel drive) is the best bargain in the A4 line. The turbocharged four-cylinder lacks the smooth, quiet operation of the V6. But it's strong enough to deliver good acceleration, particularly with the manual gearbox. A4 1.8T is about 210 pounds lighter than an A4 3.0, and seems quicker to respond. It may be the spriest of the bunch.