The acceleration will knock your socks off, with a massive 333 foot-pounds of torque at 4000 rpm to go along with the 340 horsepower. (Torque is that force that thrusts you away from intersections.) But the high-tech V8's continuous variable valve timing makes the power delivery so smooth and steady there's nothing wild about it. The best part might be catching the looks on the faces of the drivers around you, who would never suspect something that looks so pedestrian could vanish so quickly. The M45 is lighter than the Q45, which is already a fast luxury car, and its final-drive gear ratio is numerically higher than last year's Q, so flight is effortless.

The five-speed automatic transmission is superbly compatible, delivering dazzling smooth upshifts and kickdowns. It's right on the money when driving hard. At slow speeds, between 20 and 40 mph, easy on the gas, it shifts invisibly, imperceptibly. You couldn't ask much more from an automatic transmission in a car like this.

That's assuming you don't care about a manual mode. The manual mode in this tranny might as well be a write-off. But it's no great loss with the M45, which doesn't beg for its use. It's just not programmed for serious sporty use. Full-throttle upshifts have a lag time in the manual mode that doesn't exist in the automatic mode. And, totally unlike the sensational and drop-dead gorgeous new Infiniti G35 Sport Coupe (introduced at the same time), the M45 manual operation is over-ridden by a chip that shifts up and down on its own. Worse, the digital readout indicating the gear doesn't always change. In manual mode, we went from third gear to first (slowing to a stop), then to second to third (accelerating), to a final kickdown to second (passing), without ever touching the lever, and without ever seeing the number 3 on the dash change.

The brakes are big vented discs, and earn great marks. The ABS was as solid and true as any we've felt in recent memory. We made a full panic stop at 70 mph, and they were very busy, very firm, very quick and very true, with only light pulsing transmitted to the steering wheel. The M45 is equipped with Electronic Brake Distribution (distributes the braking force to the tires that have the best grip), which is always a good thing to have. It also comes with Brake Assist, which senses a panic stop and applies braking harder or longer than your foot signals.

"We pushed the suspension to the limits of control and stability," said an engineer at the M45 introduction. With 340 horses' worth of potential to get in trouble, this level of development is a good thing. It's fully independent, with struts in front and links in rear, and sport tuned. Unlike the Q45, which has three shock absorber settings from the cockpit, the M45 lives with just "firm." It's a very high quality of firmness, never harsh or uncomfortable. It erases most of the rough and patchy stuff, and stays the same degree of firm, keeping the car on an even keel no matter what the surface. You know the ride means business.

We didn't push the suspension that far, but we drove it as hard as we've driven some other luxury sedans, and it passed with flying colors. Although the track (the distance between the left and right tires) isn't very wide, the 18-inch wheels and W-rated tires help it handle nicely in the curves, and the speed-sensitive rack-and-pinion steering provided good feedback and didn't feel soft. If an Impala SS handled this well (not to mention accelerated this quickly), people would think it was the greatest car in the world.