For a supercar, being fast and grippy isn't enough, is it? A simple ability to cover the ground rapidly is no longer a USP. You can get that in a saloon. We don't hear anyone accusing four-doors like the M5 or E63 AMG of being ‘a bit slow from A to B'.
For supercars to be able to stand apart from all the hyperpowered saloons and big-money GTs, they need to add some memorable sensation to the mix. The intimate feel of the road, the holler of an engine. Or, of course, the wind over your skull.
This is why we're loving the SLS AMG Roadster. Unless you've got micro-sensitive telematics set up, we're willing to bet you won't detect any difference in straight-line or round-a-track speed compared with its tin-topped Gullwing brother. But by golly, the Roadster makes you think it's a whole other league faster.
The epic 571bhp, naturally-aspirated V8 is as timewarp fast as it is in the Gullwing. But if the fact your spleen is wrapping itself round your spine isn't enough to tell you about the acceleration, with the roof down in the Roadster you've got a direct accoustic path from the exhaust. It's an extraordinary canon of sound to go with the power. A belly-shaking, sabre-rattling roar that hilariously multiplies the sensation of speed.
And roof down, there's breeze too. Nothing drastic - there's no buffeting like you get on a four-seat cabrio. The seats are heated, and ‘Airscarf' fans blow hot air onto the back of your neck via the headrests. But it's plenty enough to amp up your impression of motion. And isn't that why we like driving in the first place?
I'm struggling for a downside. Roof up in the rain, the hood's quiet and insulating. The handling and steering, roof up or down, are as per the SLS - a proper old-school rear-drive monster, with an ESP system that wriggles quite enough to let you know you're pushing it. The Roadster's £176,895 is more than the Gullwing, but it's a trivial difference compared with the general entry ticket to SLS-land.
The Roadster makes SLS life a bit better when you're going flat-out, and that's all to the good. But far more important, it turns up the experience to 11 even when you're not.