JAGUAR has good reason to be proud of winning the latest JD Power durability award in the United States, but the press launch of the upgraded XF range this week showed they still have a lot of work to do before being truly on the same level as its German luxury car rivals.

In the course of driving three cars, we experienced a number of annoying problems – a temperamental supposedly one-touch glovebox opening, a flashing bonnet open warning light, non-operating cruise control and a persistent vibration around the cupholders.

And, while Jaguar cannot be held responsible for a puncture we suffered, it did reveal the shortcomings in the design of the jack and wheelbrace, as well as the fact that the soft-sidewall tyre was expensively ruined by the time the lack of inflation became apparent. An argument for pressure sensors, we suggest.

We also experienced some fairly crude brake graunching coming to a stop in normal traffic conditions, which was rather surprising. Combined with a last-moment grabbing – unlike BMW’s great soft-stop brakes – it made stopping less than smooth and comfortable no matter how hard you tried.

These shortcomings are most unfortunate because we truly believe that Jaguar is on the right track, with greatly improved styling, engineering and production, but this experience perhaps explains why the company is not getting complacent.

And we really like the XF overall, especially with the new range of engines introduced for 2009 (sorry, Jaguar, but it’s a bit early to call it the 2010 model year).

Starting at the bottom of the range, the 3.0-litre petrol V6 is the only engine that is unchanged just one year after launch, and was understandably not present at this week’s press preview drive (ahead of the August on-sale).

The diesel offering is quite something, the previous 2.7-litre unit being replaced by an all-new 3.0-litre common rail turbo-diesel developed in conjunction with PSA Peugeot-Citroen that takes the XF into another stratosphere. It really is remarkable how car-makers can produce more powerful engines that at the same time reduce fuel consumption and carbon-dioxide emissions.

Unfortunately, you now have to pay $6800 more for this diesel than the V6 petrol, whereas they were previously priced the same, but it really is a huge step forward in every respect.

If you didn’t know any better, you could easily think you are driving a big supercharged petrol engine because it is so smooth and quiet. There is barely a trace of diesel clatter when cold and only a bit of harshness if you take it (unnecessarily) to maximum revs.

Low-down torque – some 600Nm from 2000rpm – is, of course, very impressive and the urge continues progressively through the revs with no surge or fall-off, thanks to an innovative approach to the twin-turbo format with a smaller ‘primary’ unit. The bottom line is that climbing hills is simply a constant rush forward.

The extra power combines well with the revised six-speed automatic transmission to provide a more linear progression than in the previous diesel, which we thought was a little lethargic and unresponsive with its changes. No problem there with the upgraded XF, even in normal shift mode.

And, if you choose to use the steering wheel paddles for manual shifts, you will find they are among the best in the business, being well-placed and having a nice touch.

Most of the XF’s controls are excellent, although this indicator sits a little high for our taste and we are not convinced that the rotary gearshift knob will stand the test of time.

While most of the attention on the new XF has surrounded the new diesel and the high-performance, the new normally-aspirated 5.0-litre V8 petrol with direct-injection for the first time also deserves some attention.

Sharing the same engine architecture as the XFR’s supercharged V8, the new ‘atmo’ is something of a jewel, providing fantastic performance – seven-tenths of a second faster from 0-100km/h than the diesel – accompanied by a wonderful engine sound.

Unfortunately, as with the diesel, you now have to pay a higher premium for this great new engine, being about $13,000 more than the previous 4.2-litre V8 model at some $147,900. It is a better car to drive than the diesel model ($116,250), but perhaps not a $30K better drive.

In terms of dynamic qualities, both the diesel and V8 enjoy the excellent Jaguar rack-and-pinion electro-hydraulic steering and well-engineered suspension, which offers a reasonable balance between ride and handling (without the benefit of the XFR’s advanced active suspension system), but they similarly suffer from a little more road noise and sharp-edge ride quality than desirable.

Inside, the seats are comfortable and most of the controls, fittings and trim levels provide a welcoming and impressive environment for front and rear seat passengers alike.

There is still room for improvement in the XF and we hope this will happen for the mid-life facelift in a couple of years’ time because this stylish car deserves a place alongside the E-class and 5 Series mid-size luxury segment icons.