From where I write, sitting in a Mercedes SLS AMG beside the gullwing coupe's launch route in California, I'm being treated to occasional fly-pasts from sister cars. Usually I wouldn't scribble here; I'd write later from my notes. But during this morning, on the roads you see here and on a nearby race circuit, I've found the SLS quite hard to pin down; I'd rather nail my opinion than let it wander off again.

I've read a lot about this car without really finding out what sort of sports car it is – whether it's a GT akin to a Ferrari 599, or a more agile sportster like a Ferrari F430.

What's certain is that the SLS will have no shortage of competition when it goes on sale next June. Buyers of AMG's first complete car won't see change out of $240,000. That's Ferrari 458 Italia money but a figure that also leaves the SLS open to fire from anything from a 911 Turbo to a Noble M600, and a field encompassing Astons, Bentleys, the Audi R8 and Lamborghini Gallardo. I will be astonished, too, if McLaren later pitches the MP4-12C's camp much farther away.

None of those cars, of course, has the gullwing doors that define the shape of the SLS, as they did its spiritual predecessor, the 300 SL. It's not controversial to say the SL is prettier, particularly from the rear. This morning a pair of locals told one of my colleagues that the SLS's rump looks like a Lexus SC430's. Harsh? Perhaps. Accurate? A little. That said, though I initially reeled at the pictures, I was pleasantly surprised when I saw the SLS in the metal.

I'll be honest, though; I expected more from inside the SLS than I found, in advance of a few hours pounding some Californian highways. It's not the best place to try a new supercar, but it's a part of the world that has more than its share of them.

Mercedes talks of the SLS having an airplane-inspired cockpit, but apart from ducking under the door like you're crouching beneath a helicopter's blades, there's not too much that's avionic about it. The air vents are supposed to resemble jet engines (perhaps a four-blade prop) and the stumpy gear lever a throttle (and maybe it does). But that's it for inspiration.

The dash is square; strong horizontal lines are meant to accentuate width, but they also highlight a lack of imagination. The overall finish is fine but the choice of materials lets it down in places. The leather's great and the surfacing is classy, but the audio controls, heater controls and dials have more than a hint of silvered plastic about them. Their fonts are slightly clumsy, at once feeling both low volume yet medium quality.

The SLS's seating position is excellent, if not its visibility or access. You sit low, between a large sill and a high transmission tunnel, which makes entry tricky and closing the door trickier still.

To allow enough room to get in and out, the doors swing high (still low enough to allow a hefty whack on the head), and it's quite a stretch to reach the handle to draw them shut. Kids will have to stand. I'm sure there could've been an elegant solution involving a strap.The panel of buttons (a row of controls for powertrain and electronic aids) lined up beside the driver is neat, though. On it is the start button that fires the 6.2-liter V8, which AMG dubiously dubs a 6.3 (the company has now also taken to calling it “near-legendary,” despite the fact it's only three years old).

It's a fine engine in its normal form, but for the SLS it has been dry-sumped and given a new intake system, and much of its top end is revised. At 563hp, its power output treads a line neatly between those of its rivals, and its performance is absolutely ballpark, too. Sub-four seconds to 62mph is expected, and given. The top end is 197mph.

What is unusual about the SLS's drivetrain – not just for an AMG but for a Mercedes – is that it has a dual-clutch transmission. Mercedes calls it Speedshift, presumably to draw a parallel with the semi-automatic 'box of the same name in the SL63, which has a single wet clutch.

The new 7-speed twin-clutch 'box is a rear-mounted transaxle, made by Getrag and fitted behind a carbon fiber torque tube that weighs just 10.4lbs. You'll find the same 'box in a Ferrari California, but AMG's take on things is rather different. A lot of manufacturers will let the clutches swap almost immediately; AMG has programmed a slight delay between shifts, more in keeping with the rest of its cars.

I can't help but think it would have used a normal gearbox were it not for the fact that the transaxle gives the SLS weight distribution of 47 percent front/53 percent rear. Like the Ferrari 599 GTB Fiorano, the SLS's engine is technically at its front, but its weight is just biased rearward. The chassis is an aluminum spaceframe, on which sits an aluminum body, giving a 3,571lb curb weight for a 15ft long, 6.5ft wide supercar.

Like all AMG engines, the SLS's motor sounds terrific, albeit noisier and more gravelly than elsewhere in the range. As we trundled out this morning it struck me that, until you get up to freeway speeds, it's always audible – and even then it can be heard on anything beyond part-throttle. It's not unlike a Ferrari in that sense – and unlike other AMGs – in that the sound never goes away.

It's a glorious, mechanical sound, though, and while Ferrari V8s get a flat-plane crank and most of the SLS's rivals have more cylinders or induction assistance to call upon, don't think that the SLS's engine is a poor relation. 

Opportunities to open it up on the road are rare, but when the time comes I discover that it's a terrific motor, with a superb, linear response throughout the rev range, and it revs incredibly easily for a motor with cylinders this size. It has a better response than Aston's V12, and a delicate pop engineered into the overrun sometimes. I've watched a few SLSs being pushed hard today and the spite emanating from their exhausts is the equal of any modern car with Detroit iron. If I look away, the engine note and gentle background hubbub could be mistaken, if not quite for a NASCAR stocker, then certainly for an Aussie V8 Supercar.

At least as noticeable on the road, though, is the tire noise. I think the aluminum chassis and the stiff bushes of the double-wishbone suspension transmit a great deal of noise into the cabin. There's more than in most rivals I can think of; perhaps it's comparable to an F430, though quieter than the Scuderia. More sports car than GT levels, certainly.

As a result of its aluminum construction, the SLS's shell does feel (and you can sense it) astonishingly rigid. Like you can tell if an unsuspended mountain bike has a steel or aluminum frame, so, too, can you detect the unflinching rigidity of the SLS's body.

It has allowed AMG to set up a ride that, for all the noise, is both firm yet compliant, softer than a 911 but with better control of its body movements. Ferrari does it, too, and Lotus manages the same with the Elise. In fact, given the high sills, there's more than a hint of big Elise about the SLS.

Where it differs is in the steering, because the SLS's rack is fast and light. Initially you'd swear there was no discernible feedback, even while pressing on through the corners. It felt agile enough, and quick, but somehow unrewarding – somewhat detached, and anodyne. AMG wants the SLS, like all AMGs, to be a car people can and will use every day. But with that, I thought earlier, some of the allure surely went.

I don't think that so much anymore. When I arrived at the launch HQ this morning, I was a bit underwhelmed with the SLS. Sure, it was fast, but somehow less satisfying than the best sports cars, and not the world's greatest GT car, either.

So I drove it some more, and I drove it on track, and I drove it on the road again, and slowly it revealed its true depths. In a way it is like its rivals – it has a bit of all of them – but on a track it does almost feel like a comparative Lotus might, with that same body rigidity, yet with some roll and compliance in the suspension. The steering does channel feedback, but its signals are delicate. So's the chassis balance.

There's strong grip, obviously. It's less flighty and agile than a mid-engined Ferrari or V8 Audi R8, more willing to turn than an Aston. Traction is solid at above Aston levels, probably those of a 599 HGTE. The natural balance is toward understeer, but turn in on the brakes and the rear will unsettle a tad, either to neutrality or, with a bit of throttle coaxing, into a slide that can be held and adjusted easily. As in an Aston, the naturally aspirated throttle response and a wide range of power is a real boon here – although I suspect a big Lotus would exit the slide with a little more grace than the SLS, whose weight, while tightly controlled, still takes a moment to settle.

Carbon-ceramic brakes are indefatigable but optional. Where the SLS disappoints on the track is in the response, the sometimes sluggish and downright obstinate response, of its gearbox software, which perversely is excellently judged for the road. But that's not enough to spoil what a terrific car the SLS turns out to be on a circuit. It was as much of a revelation on track as it was a mixed bag on the road earlier.

And now, a few hours on? I'm still not totally sold on the SLS. It's excellent generally, borderline brilliant in parts. Its gullwing doors are both its raison d'être yet also a compromise that modern materials stiffness means you need not make. And the finish could be better.

At times I've enjoyed driving it as much as I've enjoyed driving anything this year bar a Noble M600. But I wonder if AMG is just asking a wee bit too much of the SLS when you compare it with, say, an Audi R8 V10 at two-thirds the price.

The SLS is a stronger car than a lot of vehicles around it, and it'll put the wind up a lot of industry executives. I'm just not totally convinced that the blend of its undisputed qualities is quite the right one.

Matt Prior/Autocar