Only a couple of years ago a fellow journalist, bored with the job of reviewing modern cars with little to complain about, stated that new cars have no character. He had a particular distaste for Japanese cars. I wonder does he still feel the same way today given the proliferation of new models and the acknowledgement by the car makers that competency is no longer enough to entice buyers. When we tested Nissan's fabulous 350Z last year we discovered a sports car worthy of the title, with buckets of personality. Now there is an open-top version branded the Roadster.

Though in the middle of a particularly good June, we didn't trust British weather to allow us to fully appreciate the charms of the 350Z Roadster, so we took it through the super-efficient Eurotunnel and drove top down at high speed to Le Mans under the cover of darkness. Three days in France on varying surfaces, and two days either side on our own test roads back in the UK were certainly enough for us to form our opinions about this new entry on the market. Would we (very much more inclined to buy a coupe version over a convertible in most cars) be tempted by a Roadster over the regular 350Z?

First, the looks, surely one of a car's most important aspects in the Roadster's class. The 350Z coupe is distinctive and brawny, a muscle-bound sports car that is unmistakably Japanese and all the better for it. Chopping its roof off was always going to be risky. Roof up, I don't think the Roadster compares favourably with the coupe. The reasons are simple: one, thanks to the high waistline, the canvas roof only has to cover a small volume, meaning it looks out of proportion to the rest of the car; secondly, without the sloping rear hatch, the rear deck of the car is, well, large. Think of Jennifer Lopez's rear rather than Rosanne Barr's though, it's still nice...

Open up the doors with the over-sized handles and you'll be greeted by the same two-seat cockpit as in the coupe, though the Roadster feels cosier thanks to the close proximity of the standard wind breaker between the two roll hoops. The attention to detail verges on obsessive, with the 'Z' motif appearing on the glass wind breaker as well as moulded into the air vent that is only visible when either door is actually open. Sadly, the fit and finish does not quite match that found in Porsche's Boxster or even the BMW Z4. The switchgear is well-placed and good to use, though it is a pity that the budget could not stretch to alloy column stalks. The instruments are quite unique, with hints of '70s Z-cars. They move with the steering wheel too ensuring the driver has a good view of them at all times, but we were disappointed to find a lack of reach adjustment on the steering wheel. The driving position reminds the driver that he is in a sports car, with the chunky gear stick near to hand and perfectly positioned pedals.

You'll want to check out the roof next, so ensure that the gearbox is in neutral, put your foot on the brake, unlatch the single central handle and press the open button. The windows lower, the sculpted tonneau cover springs open and the roof folds itself neatly under it. Being picky, I'd want the side windows to return to where they were, but more bizarrely, during this process, the passenger's seat is tilted forward by a few degrees to ensure that the roof clears his head. That's all well and good, but it doesn't work if the seat is all the way back in its runners and the process just stops. We couldn't see why it was not working when this happened first. Owners will have to look at this as character rather than a fault I feel! In place, the roof is snug, transmitting a little more road noise than the hard top, but perfectly waterproof.

Turn the ignition key and the real fun starts as the 3.5-litre V6 roars into life and settles at a purposeful idle. Here the Roadster scores big against the coupe; the engine and exhaust are unchanged, but with the roof down you are subjected to the full assault on your ears, and if you think it's good at idle, just wait until you get a chance to open it up properly. It may not be cool to admit this, but I found I had a favourite engine speed: between 3500 and 4000rpm the engine sounds positively alive, smooth yet full of menace, like the purr of a Siberian tiger just before it rips you to shreds.

Snick it into gear (incidentally, we found that the gear linkage in the Roadster had less vibration and was a little slicker than in the coupe), feed in the weighty clutch and push the long travel throttle pedal to the carpet and you can't help but grin ear to ear as the Roadster hits 62mph in just 6.4 seconds and we saw an indicated 155mph (on a private test track of course) with the hood down, all the while playing a sonorous song from its exhaust pipes. The 3.5-litre V6 has a real hard edge to it if you rev it to the redline (you can actually set the speed at which the gearchange light comes on), and the Roadster feels nothing short of ballistic if driven in this manner, but keep the revs between 3000 and 5000rpm and ride the ample torque and you will not be disappointed either, with easy fuss-free overtaking and long-legged cruising on tap. It's just as well there is this option, and a sixth gear. While testing the Z on our own tortuous B-road test routes, we managed to average no better than 19mpg. Over the course of the week, including the high-speed blast to France and back, the 350Z Roadster averaged 22mpg, which is not far off Nissan's claimed combined figure of 24.1mpg.

So it goes almost as hard as the coupe and is not really any thirstier; it looks good, if not quite as uncompromised as the hardtop. Crunch time, how does it drive? Well, taking a read through the press material hints at the amount of effort gone into ensuring that chopping the hard top off the 350Z does not ruin the car's handling. A V-shaped brace connects the sills under the seats; an A-shaped brace reinforces the front end; a 'Mizuno' bar attaches to the structure ahead of the rear wheelarches and connects to the A-shaped frame. Additionally, reinforcement has been added to the door openings, across the transmission tunnel, the sills, A-pillars and windscreen surround. Beneath the roll hoops is a significant amount of lateral strengthening and even the steering column has been reinforced and linked to the A-pillars. Results are mixed. The 350Z Roadster is still just as good to drive hard, and retains the coupe's fantastically playful rear end, with masses of grip when you want it. It is not difficult to force the rear tyres to lose a little grip when exiting tighter corners, allowing a neutral-to-oversteer lead stance. Such is the dependability of the traction that I would suggest that the traction control should be off by default, with the driver selecting it when conditions require a more sensible approach. The only other car I've recommended that for is Honda's S2000.

The Roadster is not perfect though. Despite my enthusiasm for the car I could not hide from the fact that the body's stiffness is compromised without the roof. No matter how much work has been done to reduce body twisting and nasty scuttle shake, certain roads have the 350Z Roadster shimmying around where the coupe might just be a little uncomfortable. In honesty, you are unlikely to push the coupe hard on those same roads, and to put a number on it, I'd say that the Roadster provides 90% of the coupe's chassis' abilities.

If you can do without that last 10% in return for an even more arousing and accessible exhaust note and a neat, quick folding hood then the Roadster will not disappoint you one jot. Bear in mind though that this is no anodyne sports car. It has faults too, though today I am happy to call them distinguishing characteristics.