I have an immediate choice of two McLaren 650 Ss to tackle the magnificent roads around Loch Lomond and am therefore one of the more fortunate holders of a driving licence in the world today.It seems reasonable to write a review about the more popular one. This, by no small margin, is the Spider convertible, which outsells the fixed-roof Coupe by more than four to one. So, McLaren, I'll have the Spider, please.Normally I would have a problem with this. I don't like convertibles. I do not enjoy having the wind in my hair when I'm driving, but more than that I object to the structural sloppiness which results from cutting off the roof of a car that was designed to have one.Ah, but, you see, the 650S wasn't built that way. It is based on a carbonfibre tub which, incidentally, is the only part of the car not created in the UK. This work has been subcontracted to a company in Austria because although there are plenty of carbonfibre experts in this country none of them has the capacity to build as many tubs as McLaren needs.And, to get back to the point, the tub is the structure. The roof of the Coupe is not important in this context, and making it retractable to create the Spider makes no difference. The two chassis are equally strong, equally stiff.Within a few minutes it has become apparent that the 650S is a brilliant car in so many ways that it's difficult to know which to mention first. Let's play safe and start with the most obvious one: with an engine producing up to 641bhp and the kerbweight of a Ford Focus, this car is madly fast. You can get from a standstill to 124mph in under nine seconds. 0-186mph takes less than half a minute. The overtaking potential is so great that you might find yourself passing vehicles you hadn't even seen when you began the manoeuvre.On full throttle and at high revs the acceleration is startling and stirring. Once you have felt it, you are no longer the person you were before. The engine note isn't the most inspiring in the world, and it tends to be obscured by wind noise as the speed rises if you've put the roof down, but it does make an important contribution to the whole rousing experience.Cool, huh? But a colleague makes a good point. The performance, he says, is no more than the fifth most important thing about the car. We don't bother establishing what the four ahead of it might be because it doesn't matter - the principle is correct. If the 650S were all about speed, it would be fun for twenty minutes and then you'd want to hand it back. I've driven it for two hours and I don't think I will ever want to get out.The 650S has turned out to be a replacement for the 12C, but it was originally intended to be a sharper, more aggressive version of it, intended to please those who feel that a supercar should be a bit of a beast. I'm not sure how impressed those people will be with it, because for me its outstanding feature is how it does everything efficiently, smoothly and without the apparently requested edginess.Take, for example, the steering. As you manoeuvre out of a parking space at less than walking speed the 650S already feels like a racing car, going exactly where you point it. And it continues to do that almost no matter how quickly you want to go. It feels just the same even when being urged along a road whose name - Hell's Glen - gives some idea of how challenging it is, though not of the throat-catchingly beautiful scenery.But there is no race-car abruptness. Changes of direction are as rapid as you want them to be, but they are not sharp-edged. It's as if the car pours itself into a corner, which is elegant, rather than darting towards it, which would be barbarous.The suspension set-up is a wonder. I'm told that McLaren engineers are proud of what a range of abilities this car has across its three driving modes - Normal, Sport and Track. I'll go further than that on their behalf. I would be proud of how capable the 650S is on a wide variety of roads even when you leave it in Normal.How comfortable do you think the ride quality could possibly be in such a car? It's more comfortable than that. Not quite luxurious, but not far from it, and almost shockingly better than that of many a much more conventional car fitted with wheels and tyres it was never designed to wear (and there are far too many of those).And yet the same set-up which makes this possible also allows me to blast out of a tight uphill hairpin on nearly full throttle in first gear with no drama at all, other than the tremendous acceleration of course. You can feel the back end adjusting itself in accordance with the road surface and camber, but it doesn't step out and the tyres don't complain. If any of this happened, the 650S would feel more exciting than it does, and some people would admire it for that, but it would not be such a good car.The brakes - good Lord, have you seen the size of those discs? - are absolutely in tune with what has already been described. You are going very quickly. You need to stop. You've stopped. You should feel as if you've just driven into a cliff face, but there was nothing to it, apart from that smell of something hot which wasn't there a few seconds ago.Funny thing about the brake pedal, though. It's placed further away from the throttle than you might expect, as if McLaren expects you to operate it with your left foot. In a high-performance car with no clutch pedal that's a perfectly sensible way of doing things, but it feels strange if you're not used to it.Since a critical note has now been sounded (and you'll notice how long it took for that to happen), here are some other things that puzzle me. Why has the footrest been position and angled so that only my toes can comfortably reach it? I'd rather my entire sole could be in contact with it, but it takes effort to make this happen and there should be none of that.And although the way the doors open upwards as well as outwards is sexier than sex, and a source of fascination to the onlookers who inevitaly gather round the car every time it stops, I'm concerned about whether or not I could get out if I were unlucky enough to park it on its roof. McLaren says there are no reports of anyone having a problem with this, but perhaps that's just because no one has yet upended one of its cars.The pricing of the optional extras could make sense only in a world I do not inhabit and probably never shall. There's an upgrade pack which includes carbonfibre versions of the fromt splitter, door splitters and rear bumper. You can have that for £8470. If you go really wild with your carbonfibre choices you could easily pay upwards of £35,000.To put that another way, it's possible to spend more than the list price of a Jaguar XF simply to make your McLaren distinctive - or perhaps not all that distinctive, since this is common practice among 650S customers and your car will end up looking much like theirs.Of course I'm missing an important point here. The advertising executive and behaviour economics populariser Rory Sutherland has said - rightly, I think - that a vehicle does not function as a status symbol merely because it expensive. If that were true, long-distance lorry drivers would be the most attractive drivers in the world. It must also, like the peacock's tail, be useless, and although all that carbonfibre stuff reduces the car's weight, it doesn't do so to an extent that will be noticeable on the public road.So it's as near useless as makes no difference, and therefore, paradoxically, useful in terms of showing off the owner's status. And, frankly, if you can afford a 650S you can afford to spend an extra £35,000 on it. You'll probably spend a lot more - McLaren can't be faulted for giving its customers many opportunities to do so, and in general they respond enthusiastically.This does not sit well with me any more than the idea that a supercar should be awkward and demanding. I want a 650S for quite a different reason: talented engineers have been encouraged to do their finest work, and driving this tribute to their various accomplishments makes me very, very happy.The mood soon passes, but as I approach my destination I briefly wonder if I will ever want to drive another car, having now driven this one. Engine 3799cc, 8 cylinders Power 641bhp Transmission 7-speed semi-automatic Fuel/CO2 24.2mpg / 275g/km Acceleration 0-62mph: 3.0 seconds Top speed 204mph Price £215,250 Details correct at publication date