Infiniti's full-size SUV handles quite well for such a big vehicle. There's a modicum of body lean in corners. The steering feels precise, with good variable assist. The combination of comfortable ride and responsive handling comes from the four-wheel independent double-wishbone suspension with front and rear stabilizer bars. The independent rear suspension improves ride and handling on rough roads. It especially helps smooth the ride for those seated in the second and third rows.

An advanced rear auto-leveling air suspension (which comes standard) improves stability and ride comfort when towing or hauling cargo. The air suspension maintains a uniform ground clearance and departure angle by automatically adjusting the air pressure in the suspension's air bladders. The QX56 is rated to tow up to 9,000 pounds with 2WD or 8,900 pounds with all-wheel drive, more than the 2006 Cadillac Escalade (8,100 pounds) or Lincoln Navigator (8,600) or Toyota Sequoia (6,500).

Nissan's 5.6-liter, 32-valve, double overhead-cam V8 offers impressive output, rated in the QX56 at 315 horsepower at 4900 rpm and 390 pound-feet of torque at 3600 rpm. That easily trumps the Sequoia's 282 horsepower and 325 pound-feet of torque. The Lincoln Navigator, impressively revised for 2005, offers 300 horsepower and 365 pound-feet of torque. The 2006 Cadillac Escalade has a 6.0-liter overhead-valve V8 that boasts 345 horsepower at 5200 rpm and 380 pound-feet of torque at 4000 rpm, but note the higher rpm. (An all-new Escalade is being introduced for 2007.) Towing demands high torque at low rpm and that's where the Infiniti's power is concentrated.

Acceleration performance is strong, but less than sparkling. The most likely reason for this is weight: An Infiniti QX56 AWD tips the scales at 5,631 pounds. That's slightly heavier than the Cadillac but a little lighter than the Lincoln. Nissan's overhead-cam engine sounds good, though, producing the appropriate big-V8 exhaust tones when you mash the gas.

Braking is solid and linear, with good, manageable pedal feel. The QX56 features four-wheel disc brakes with ABS. The antilock brake system is barely felt when called upon and allows the driver to maintain steering control under hard braking. Electronic brake-force distribution (EBD) improves stability under braking, while Brake Assist helps the driver get maximum braking performance in an emergency stopping situation. The electronic stability control system intervenes when the QX is pushed beyond the limits of grip, driving too quickly into a slushy corner, for example, and corrects the imbalance with little excitement.

Perhaps Q stands for quiet. Very little tire and road noise invades the cabin, thanks mostly to abundant sound-deadening material. Some wind noise is unavoidable, given the roof rack complete with cross rails, but it's reasonably muted.

The QX56 is available with rear-wheel drive or all-wheel drive. The AWD system offers 2WD, 4HI and 4LO modes. A two-speed electronic transfer case allows the driver to select low ranges for 1st, 2nd and Reverse gears for seriously rugged terrain. The AWD system is designed to instantly distribute torque to all four wheels as road conditions warrant. Under normal driving conditions, the system operates in rear-wheel-drive mode for optimum fuel economy. But when conditions warrant, up to 50 percent of the power is transferred to the front wheels on demand, resulting in optimum traction. All AWD QX56s include heavy-duty skid plates for the oil pan, fuel tank and transfer case.