KIA’S new Optima was a smash hit last year in the US and Korea, where it was the nation’s top-selling D-segment model bar none in June and July, and now we know why.

We’d already been impressed by the car’s sleek lines at motor shows, where the Optima’s concept car-like proportions, attention to detail and plethora of unique design elements convinced us it would be a stand-out even in the star-studden medium sedan class.

From the striking Schreyer signature grille, the shape of which is echoed by a unique windscreen shape, to the classy lower grille with foglights and LED daytime running lights, the Optima has the sort of road presence many fleet-oriented medium sedans would die for.

And that’s without seeing the chromed side window surround that draws an arc from bonnet to boot, the upward-sloping lower rear window line, the front quarter guard vents, the subtle but effective rear bootlid lip spoiler, the full-phat flush-faced 18-inch alloy wheels, the LED side repeaters and tail-lights, the high-gloss black A and B-pillar treatment to match the all-black roof with three sunroofs, and the dual chromed outboard exhaust outlets…

Surprises and delights continue inside, where the fully-featured cabin is dominated by a luxurious cockpit-style dashboard with a centre stack that’s angled towards the driver by 10 degrees.

Out back, there is class-leading legroom for rear passengers but, although the centre floorpan tunnel is a surprisingly low 32mm high, centre rear Optima occupants sit high on a hump that makes headroom even tighter than in the outboard positions.

Yes, the boot is huge, augmented by a split/folding rear seatback and houses a full-size alloy wheel, but out-dated gooseneck hinges will impinge on the Falcon-rivalling 500-litre-plus boot space.

The extensive range of standard features is too long to detail here and is covered in our Optima product story, but rest assured almost every important equipment base is covered by Kia here – and then some.

Soft-touch surfaces abound on the dash top and doors, there are big oddments and bottle holders in all four doors to compliment the big glovebox and under-armrest centre console, and overall fit and finish is impeccable.

Stand-out features include the classy and programmable TFT trip computer display between the easy-to-read instrument dials and the handy colour reverse camera display in the rear-vision mirror, while attention to detail is obvious in features like the lane-change indicator function and auto up/down function for both front windows.

Like the Hyundai i45/Sonata upon which it is based, the Optima’s 2.4-litre petrol four delivers solid bottom and top-end performance and never sounds loud or coarse – even at its 6000rpm-odd cut-out – but doesn’t have midrange response worth writing home about.

Playing with the intuitive steering wheel shift paddles, which thankfully override the slick six-speed transmission’s Drive mode, results in more satisfying progress on the open road, however, and our Optima returned good average fuel economy of 9.0L/100km despite a spirited mountainous drive out of Melbourne through the bushfire ravaged Victorian towns of Marysville and Kinglake.

Look beyond the undeniably upmarket styling, super-high specification level, solid engine performance and efficiency and gob-smacking value equation, however, and it is the Optima’s well-sorted chassis and superb overall refinement that could seal the deal for many.

Yes, we were one of the handful of media outlets that complained about the i45’s shocking steering kickback and rack rattle following that models launch last year, after which Hyundai was quick to react by releasing an updated MY11 model with revised damping.

Determined to leave no stone unturned for its all-new luxury sedan flagship and keen to repeat the sales success of the locally tuned Sportage, Kia said it embarked on a comprehensive Australian chassis development program well before any i45 press articles emerged.

The result of several months of local testing by local automotive tuning outfit Gambold Testing Services is improved body control and round-town ride comfort compared to the Korean-spec model, which was deemed too soft for Australian conditions.

GTS chief Graeme Gambold said his company and a Sachs engineer tried more than 20 different types of Sachs high-performance dampers and a number of anti-roll bars before arriving at a set-up that is said to deliver 55 per cent more front roll resistance and 110 per cent more rear roll resistance.

Although Kia admits there was less room to move when it came to coil spring selection, there result is slightly less bodyroll than the i45 without any discernible reduction in ride quality, giving the Optima an almost perfect ride/handling balance.

There was also local tuning for the hydraulic power steering system, a similarly unique valve setting for which aimed at reducing assistance by 10 per cent at speed and 20 per cent on centre.

The result is steering that some may find firm at low speed but delightfully pliable on the open road, where the Optima feels as alive in your hands as class-leading performers like the Mazda6.

However, while the Optima is free of the pronounced steering rack rattle the i45 suffers from, there is still a level of kickback over mid-corner bumpers. The level of deflection is never uncontrollable, but increases with the amount of speed and steering lock.

Compared to the original i45, however, the Optima is a real driver's car that bears almost no resemblance to its closely related Hyundai cousin. Kia's local development program has done wonders for what is a solid platform blighted only by under-done steering.

With that now sorted in the Optima, we wouldn't hesitate to recommend Kia's latest surprise package to anyone looking for unrivalled value in a handsome mid-size luxury sedan.