I've just tried an Active Steered 5-series on a tight slalom: flick left, flick right, easy and tidy and barely a crossing of arms. Now I'm in an Inactive Steering version (that particular term is not in BMW's buzzword glossary), and what an effort it is: twirl, twirl back, try to keep up, discover that there's little chance of that happening.

This is one of the new Five's five major talking points. The others are the looks (a bit of recurring theme currently at BMW), the semi-aluminium construction, the Dynamic Drive active anti-roll system from the 7-series and an optional head-up instrument display of hitherto unseen visibility as long as you're not wearing polarised sunglasses. Come to think of it, three out of the five are options; the styling and the construction come as standard.

So we'll begin with this latest module in the BMW design language course. The Five is calmer and rounder than the Seven, with come-hither eyes instead of glowering ones, but again the boot looks as though it's a box stacked on a sloping tail. The bootlid's shutline, following the rear pillar's angle and defining the tail-lights' wraparound, is a compromise you just don't expect in a BMW. From a rear three-quarter viewpoint it's consistent enough as it meanders over the flank, but from the front three-quarter those contours render it thick then thin, as if badly repaired post-accident. 'It's impossible to do it any other way,' admits design chief Chris Bangle.

After a while, the Five does grow on you. We may yet learn to like it. There's plenty of that concave flame-surfacing stuff around arches and flanks, and it does boldly go. Bangle may yet be right.

Now, this part-aluminium. It's the front part, up to and including the scuttle but not the bulkhead. It's glued and riveted to itself and the main steel hull, and incorporates cast front suspension towers like a new Jaguar XJ's. Why? Weight-saving in part - the new Five is 55kg lighter than the old one - but more particularly BMW's 50/50 weight-distribution mission. That's why BMW hasn't gone further and used aluminium for the doors and roof, items broadly balanced either side of the centre of gravity. Powertrains and suspension are much as before, incidentally, except that all transmissions are six-speeders.

I enter the cabin with trepidation, because there's a big silver iDrive button to battle with. But it's a cut-down, simplified version of the multi-layer muddle that is the Seven's interfaze, and I love the stereo. You can make the tuning display show an analogue-age scale, or an array of available stations like the evocative names spread across the glass panel of Granny's steam radio.

The dash itself is a mixture of old Five and new Z4, curved yet angular and refreshingly simple. There's little of the 7-series clutter here, and we have a regular handbrake and gearlever. Rear passengers will like this new Five, too, because there's a lot more room.

This is a 530i, with the usual 231bhp and 221lb ft of torque. It's not quite the engine I expected, though; the fire goes out when trying to haul out of an uphill bend, it's a touch raucous when revved and is this a tingling I feel through the controls? There's a yawning gap between second and third, too, despite the generous ratio-count. But the suspension is coping well with some imperfect surfaces, only hefty transverse ridges showing up the limitations of the optional, rubber-band-shod 18in wheels.
In particular, body-roll is close to non-existent. There's a neat trick in the Dynamic Drive, by the way, which stiffens the rear anti-roll bar more at low speeds for better pointability, the front one for better stability when cracking on. But the steering is much more startling. By 75mph it has settled into low-geared mode, slightly lower (20 to one) than the standard system (18 to one). At its quickest the ratio is 10 to one - twice as responsive - but there's more to it than a speed-related change, not least because the ratio can fine-tune itself mid-manoeuvre.

The system uses an epicyclic geartrain in the steering column, whose annular gear is powered by a worm-drive motor to exaggerate or reduce the steering wheel's movements as seen by the rack. Neat, but simple; the clever part is the programming to make it feel believable. It's also linked to the Dynamic Skid Control: if you're in a slither, not only does DSC intervene with the usual brake and throttle modulation, it also gets the steering to take part.

That's why, even when you're asking the understeeringly impossible of the front tyres in a tight corner, they barely squeal. They've been straightened, and the brakes are doing the work. Part of the route is tight and twisty and the BMW is diving, flicking round the bends like a hot hatch until, eventually, the realisation of the mass rushes up on you and systems gently intervene. You tend to apply too much steering input at first, but it's surprising how quickly your expectation curve modulates to match the BMW's. And if it detects that you're already on the case with your corrections, the DSC stands back.

The Five's not so good on a fast straight, though, where it feels like there's always a crosswind even when there isn't. BMW's engineers are aware of the problem. And that engine? I drove another 530i that was much creamier, so it's probably not an issue. That car had the head-up display, focusing 30m down the road, but I found it distracting.

I also drove a 530d: 218bhp but a lovely 369lb ft. It was a smooth-shifting auto, but a manual would really have made the most of its mighty thrust. A 520i, 525i and a V8 545i will follow; for now the turbodiesel could well be the boss.

So, is the fifth-generation Five still the keen driver's upspec exec of choice? It is, more so than ever. An M5 with Active Steering... hmm... interesting.