We haven't driven the four-cylinder version, but based on experiences with the smaller 9-3 it's stout and responsive but a bit more peaky. The turbo V-6 makes its peak torque of 285 pound-feet at just 1,850 rpm, which means it should be able to respond solidly either just off a standing start or pull strongly from near the bottom of each gear—and it does, but this engine behaves more like the turbocharged engines of a decade or more ago: Step your right foot down, and there's a slight rubber-band-like pause before the power comes on with a whoosh. You adapt to it quickly, but it's not at all like the nearly instantaneous power delivery you get from BMW's excellent turbo V-6.
Steering is surprisingly good—well-weighted, with a nice, natural feeling on center and a precise feel, even if there isn't any feel of the road or adhesion. For a vehicle that's primarily a front-driver, we didn't expect much, but the 9-5 is easier to position and plant in tight corners than many other luxury sedans. Go full throttle even with the steering off-center, and the wonderful weighting is lost, but it's still very easy to control.
The balance between comfort and responsiveness is among the best we've encountered in sport-luxury sedans here; just to the right of your knee is a dial with three modes: Comfort, Intelligent, and Sport. The simple setting controls throttle, shift points, and steering feel, as well as the continuously variable real-time suspension damping system. Both in steering and in turn-in, the difference between Comfort and Sport is noticeable, yet we were happy to leave it in Intelligent for most of the time; transitions were smooth and the system was unobtrusive, bringing the best of both modes.