The new BMW X5 4.6is is amazingly quick for an SUV. It's quick for a sports sedan. Most important, it's comfortable going up against a Mercedes-Benz ML55 AMG. And the X5 4.4i is right behind them. According to BMW, the 3.0i automatic accelerates from 0 to 60 mph in a quick 8.6 seconds, the 4.4i in a very quick 7.4 seconds, and the 4.6is in a startling 6.5 seconds. According to Mercedes-Benz, the ML55 AMG takes just 6.4 seconds with 342 horsepower and 376 pounds-feet of torque.

The 4.6-liter V8 makes terrific sounds when hard on the gas. Around town, it's quiet and very smooth, very responsive.

Power from the 4.4-liter engine is seamless, with redline coming at 5800 rpm.

Shifting is also smooth, silky smooth in normal driving situations. The five-speed Steptronic transmission can be used like a stick, downshifting with a snick or two of the lever for turns, sometimes instead of braking. It's engaged by notching the lever to the left, which puts the transmission into Sport mode, and the upshifts/downshifts are accomplished by a simple quick nudge of the lever forward or backward. Not all manual-automatic transmissions lend themselves to practical or convenient use, as the lever action may be awkward or the engine's powerband doesn't care, but the X5 is made for it, and the execution is perfect. It's wonderful to use during passing on two-lanes, making that move safer and smoother.

Handling is stable and comfortable, with less twitching and head toss than the Mercedes-Benz. The Mercedes uses body-on-frame construction, whereas the BMW utilizes a unit-body, the latter better for on-road handling and ride quality. That's not to say the X5 is soft. It feels firm in the twisties and at high speeds. It can be driven like a sports car. This firmness can make it feel jouncy, particularly when traveling at low speeds over a bumpy road while holding onto a hot cup of coffee.

On the freeway, the X5 changes lanes with the lightest of touch and with total precision. Compared to the Mercedes ML430, the X5's track is one inch wider and it rides 2.2 inches lower.

This is likely the best handling SUV on the market. Other vehicles you drive will prejudice your opinion as to its handling. If you get out of a regular truck-based SUV and get into an X5 you'll be amazed at its handling. If you get out of a BMW sports sedan, however, you'll find the X5 is not as confidence inspiring. BMW says its test drivers have driven the X5 around racetracks at speeds close to that of the 328i sedan. This is probably true for experienced drivers, who know the limits of themselves and the vehicle's capability, but for ordinary drivers the X5 is a tall vehicle; it leans more going through corners than a sedan.

X5's straight line and freeway manners are great. It feels stable; the steering is even better than in the 5 Series and the ride is smooth. The V8 engine provides plenty of power, making it faster in the race away from traffic lights than most cars. The automatic transmission offers the Steptronic mode, which turns it into a clutchless manual transmission. This is a wonderful system for those who want an automatic with manual control.

Huge four-wheel disc brakes ventilated in front incorporate every electronic trick known to man. They are easy to modulate, and, they enable the X5 to stop as quickly and securely as the BMW 7 Series luxury cars. The 4.6is model gets bigger brakes and the rear brakes are ventilated; add the super wide tires and this thing really stops.

The X5 3.0i is available with a manual transmission. That sounds sporty, but we didn't like it. Clutch engagement is quick and the torque characteristics of the engine, a bit abrupt at throttle tip-in, make smooth, brisk takeoffs a challenge. Lose concentration for a moment, get in a hurry, and it's easy to stall it at intersections, annoying because the power-adjustable steering column starts moving while you're trying to restart it. And it doesn't seem easy to use good smooth driving technique when braking and downshifting for corners, then accelerating out of them. A good driver may find it challenging to drive the X5 3.0i smoothly. A poor driver, one who moves the steering wheel about unnecessarily, will make his passengers uncomfortable with head toss. The 3.0i accelerates from 0 to 60 mph in about 8.6 seconds with the automatic; it'll do that in about 8.1 seconds with the manual and an experienced race driver. At times, the ride quality in a 3.0i felt annoyingly firm and bouncy while running errands around town; suspension undulations and head toss seemed excessive. But as we understand it, the suspensions of all three models are essentially the same, though the 4.6is is calibrated differently.

Heading off the highway in an X5 is fine, just don't attempt the Rubicon Trail. The X5 is not designed for serious off-road use. However, in a drive through a muddy test track, it proved capable of staying on course and not getting stuck.

The X5 comes with a permanently engaged all-wheel-drive system that is more akin to one found in sedans. It does not use a transfer case and does not offer low-range gears. But the X5 is loaded with electronically controlled systems to assist it in bad traction conditions: ASC (Automatic Stability Control), DSC-X (Dynamic Stability Control), CBC (Cornering Brake Control), DBC (Dynamic Brake Control), ADB (Automatic Differential Brake), HBA (Hydraulic Brake Assistant) and HDC (Hill Descent Control). There is not room to explain all this alphabet soup here, but it works. Although the X5's all-independent suspension is the key to the vehicle's ride and handling, an important part of the X5's handling capability is the use of electronic stability programs. Much of this technology is already found on BMW sedans, while other systems are new to the X5. For 2002, the system has been programmed to detect when a trailer is hooked up and to take appropriate action if the tail starts wagging the dog.

Hill Descent Control, a superb system developed by Land Rover, controls the brakes automatically as the vehicle descends steep grades; this provides an eerie experience as you can steer the X5 down a slippery slope without having to touch the brake or gas pedal. Hill Descent Control keeps the wheels from slipping and prevents the vehicle from going too fast for the conditions. When HDC is engaged and operating, the speed of the descent can be controlled by pressing the plus and minus buttons on the cruise control.