With an air suspension that can be adjusted to varying levels, the S550 rides with soothing composure. The BMW 7 Series is firmer, and the Jaguar XJ is downright stiff in comparison. It's even more impressive given our test car's 19-inch wheels, which come with the Sport package (suspension tuning is the same). Driving just gets easier: You don't have to think about avoiding manhole covers or street-side ruts. The S550 packs them off to some distant universe where alarm clocks, mass emails and other annoyances go to die.

Over stretches of uneven pavement, the car maintained remarkable control. There's minimal wheel hop, good steering response and very little suspension float. That's often a downside for soft-riding cars, and it's nice to see Mercedes sidestepped the tendency. Activate the suspension's Sport mode — distinct from the transmission's Sport mode, activated via another button — and a few more bumps seep up to the cabin, but it's not rough by any means. On the downside, body roll on curvy roads is noticeable in either suspension mode. An active suspension feature, which forcibly counteracts body roll as it occurs, is available in Mercedes' optional Active Body Control. We've evaluated a few other Mercedes products that have it, and it keeps things impressively flat on curves. ABC is optional on the rear-drive S550 and standard on the S600, S63 and S65. It's unavailable on the S400 and all-wheel-drive S550.

The S400 and S550 without ABC have silky-smooth steering. The wheel turns with light effort at low speeds, though there's a tad too much power assist at highway speeds for my taste. On sweeping curves, the car handles well. With little of the nose-heavy push that some Mercedes cars exhibit, the S550 displays enough balance to slide the rear and rotate the car with the accelerator. The XJ has better precision, but the S-Class is no turkey.