Let's make one thing crystal clear right from the outset. The S5 is not Audi's take on the BMW M3. In a market where premium sports coupes are big business, the S5 has an equally tough task on its hands dislodging rivals such as the BMW 335i and the Mercedes CLK350. It comes with a significant advantage over many recent Audi models though. The key is what Audi call the MDS platform, and it forms the underpinnings of the A5 as well as the next A4, A6 and A8 models.

The important thing about this chassis is that Audi's engineers have shifted the front axle as far forwards as possible and shunted the engine and gearbox as far back as they can. For years, chassis engineers have known that bringing weight to the centre of the car improves its responses and agility, which is why Formula 1 cars and all serious supercars have their engines mid-mounted. Bringing the centre of weight between the axles helps the S5 score points with serious drivers and details like that count for a lot. A perceived lack of credibility is a killer in this sector.

Audi has recently become a little less dogmatic in its approach to quattro all-wheel drive. For a long time, the company insisted on a 50:50 split between front and rear axles that usually gave the feel of a rather bland front wheel drive car for most of the time. The S5 abandons that position, with 40 per cent of torque being directed to the front wheels and 60 per cent to the rears. The steering system has been redesigned to offer better feel, five link front suspension helps optimise balance and that engine has been shoved way back in the engine bay. All good signs.

So what'll the S5 do? Give that 4.2-litre V8 FSI powerplant the full beans and you'll see 60mph in 4.9 seconds thanks to that monstrous 440Nm of torque from just 3,500rpm. That's over half a second quicker than the BMW 335i with which it shares a 155mph electronically-limited top speed. The sports suspension means better body control through corners and the closely-stacked six-speed manual gearbox offers real tactility. Uprated high performance brakes with black painted callipers help rein in the V8's excesses.

"Despite the massive engine on board, the S5 comes across as a more mature proposition than it first promises"

Leaving aside its radically improved chassis, the most significant factor for most buyers will be the simple fact that here at last is an Audi coupe that real people with legs and a head will be able to sit in the back of, something that could never really be said of the TT. Despite the attraction of the TT's styling, this one caveat was enough to send many potential buyers down the road, only for them to return with Mercedes CLKs or, more frequently, BMW 3 Series coupes. The S5 will seat four adults in reasonable comfort and still leave room for 455 litres of boot space.

The styling is reminiscent of the Nuvolari concept car, first shown in 2003, albeit with a good deal more shape in its flanks, the wavy beltline that runs from the headlights right back to the tail lights being the car's most distinctive feature. Nineteen-inch alloy wheels are a standard fit on the S5 and there are also twin exhaust pipes on the left and right side of the car finished in rolled chrome. The subtle S spoiler kit differentiates the S5 without being overly shouty.

Casting around the market for fast, premium sports coupes, it rapidly becomes apparent that the Audi S5 offers serious value for money. Let's take a look at a few of the alternatives that you could plump for if £40k is your budget. Key among them is the BMW 335i in M Sport specification which is around £4,000 cheaper than the Audi. Good as the BMW is, it's not quite as special as the S5. The engine relies on turbocharging to get the job done and it looks rather similar to versions costing £10,000 less. By contrast, the Audi looks as if it costs £10,000 more than its £39,825 list price. The Mercedes CLK350 in Sport trim weighs in at £5,000 more than the Audi and is now just starting to look a little old. So the S5 sits square between its two key competitors in terms of price but offers more engine and a more upmarket feel than both.

Standard equipment on the S5 includes nappa sports seats with electric adjustment and lumbar support, carbon fibre interior detailing, a multifunction steering wheel, and aluminium sill finishers with S5 logos. Options include a revised Multi Media Interface with DVD satellite navigation and a smart key that can store servicing information.

If there's one thing we can take as read with Audi coupes, it's a strong residual value. The S5 will, as a genuinely new and not merely an evolutionary product from Audi, also enjoy the benefit of being perceived - rightly or wrongly - as a more modern product than its CLK or 3 Series rivals, with this perception helping to beef-up used values. Great news if you're looking to buy one or lease a car for, say, three years but possibly not what you'd want to hear if you were holding out for a bargain on a low mileage example. Word is there won't be too many screaming deals to take advantage of.

Fuel economy is the one major black mark against the S5. There's no getting around the fact that the 4.2-litre V8 is a bit of a hog and if you can return 20 miles per gallon, you can count yourself extremely lucky. Fifteen or sixteen miles per gallon of unleaded is a more reasonable average if you enjoy giving the powerplant its head. Insurance is also likely to be pricey.

Aside from its prodigious thirst, there's barely a weak point in the S5's arsenal. Those looking for more dramatic styling might not be overly impressed by its rather low-key approach but this is a car aimed at those who want to get from A to B quickly, unobtrusively and with impeccable composure. The only problem with this approach is that those criteria are already met by the four-door S4, a car that offers more practicality and a more affordable asking price.

There is a compelling strand of logic that says that if you're going to suffer the relative impracticality of a coupe bodyshell, at least get a big payback in terms of styling. The S5 is handsome but not instantly striking. Let's call it a slow burner in that regard. Despite the massive engine on board, the S5 comes across as a more mature proposition than it first promises. Beautifully built, impeccably engineered and sweetly-styled it doesn't grab you at first, instead offering plenty for the longer run.