The FX35 launches impressively from a stop, likely because its 280-horsepower V6 makes 270 pounds-feet of torque at 4800 rpm, the same as the 350Z sports car and substantially more than other V6 SUVs. Approaching higher speeds, the 315-hp FX45 pulls more strongly than the FX35. The price for this performance is 15 mpg on the EPA's city cycle, while the V6 model returns 16 mpg. Top speed in both models is governed to 130 mph.

All of this power is managed with sophistication: The available all-wheel-drive system is tuned for paved roads. All power is sent to the rear wheels until slip is detected, and then it is gradually transferred to the front wheels. You can manually lock the front and rear axles together, or you can let the electronics do it for you. The standard electronic stability controls, which brake individual wheels to control vehicle attitude, engage so gradually we couldn't detect when they were working. That means the driver makes the big decisions, such as entry speeds into a corner, and the car decides the little things, such as the optimum braking for each wheel to keep the car doing what the driver wants.

Driving our FX45 test car on the twisty two-lane sports car roads circling the Red and Black Mountains in Southern California, we were still able to induce a slight amount of power oversteer while cornering, although we were never able to break the mammoth rear tires loose.

In tight and sweeping corners alike, the FX45 rode incredibly flat, which is the plus side of having such a stiff suspension. We pushed the FX45 hard, and didn't give it a break because it was an SUV. Understeer begins very gradually when you aim the FX into a corner, and the front wheels continue to push only slightly until you get near the FX's very high limits. Like the 350Z sports car, the steering is quick, but it doesn't feel as telepathic as a Porsche's. Nor does it feel like the light-and-loose feeling you'll experience in any other SUV, including BMW's X5.

Infiniti claims the FX will brake better than rivals from Mercedes, BMW, and even Porsche. Our FX45 test car was confident under heavy braking, and that allowed us to drive it very quickly without any scary moments on twisty roads, but there's no question there's a lot of size and weight here.

Our FX45 was as much fun to drive as most sport sedans, but the price is the stiff ride. On long stretches of freeway, the FX45 is relaxed, and our test car cruised at 80 mph in fifth gear with the engine turning just 2850 rpm. Our FX45 wasn't as quiet and isolated as some luxury cars, and although our test car's cockpit was quiet enough to hold a delicate cell phone conversation on an empty highway, we'd never describe it as a serene environment.