Midsize luxury cars run the gamut from comfortable to rigid; the M is closer to rigid, though not so much that it's punishing to drive. Despite my test car having the Sport package — which augments the four-wheel-independent suspension with sportier tuning, bigger wheels and high-performance summer tires — ride quality was livable. Highway road noise remains tolerable up to 75 mph — above that, wind and road noise quickly encroach — and the car's chassis dispatches bumps with modest noise and few reverberations.

If you live near curvy roads you'd do well to drive them in the M. The steering wheel moves with a lighter touch than in Infiniti's smaller G35, and though it doesn't feel as precise in prolonged bends — highway cloverleafs, curvy backroads — the turn-in precision for lane changes and most city driving is in the same league. All told, the steering feel encourages twisty-road driving in a way a Volvo S80 or Mercedes E-Class cannot. Body roll remains well in check, and at its limits the M displays good grip and even better balance. The Sport package adds Infiniti's Rear Active Steer, which power-adjusts the suspension hardware to angle the rear wheels slightly while the car is turning. The purported result is swifter handling. I couldn't tell when the system was operating — or what benefits it added — but the M never once came off as unresponsive, so evidently it did its job.

Naturally, models without the Sport package probably display different ride and handling characteristics. All-wheel-drive models increase the M's turning circle to 36.7 feet, as opposed to 36.1 feet with rear-wheel drive. Those figures are right on par with the competition. The rear-wheel-drive Lexus GS carves the narrowest circle, at 34.1 feet, while the V-8 Volvo S80 trails the segment at 40.0 feet.