You wouldn't have thought that cars could suffer from schizophrenia, but the new Mercedes does seem to be a victim.
Consider the evidence. This is a car that is fitted with a 518bhp V8, rear-wheel drive, and thoroughly clever not-quite-a-DSG-but-close 7-speed transmission (of which more later). It can also hit 62mph from rest in 4.5 seconds.
And yet it is a car that seems desperate to play the role of normal executive saloon. Put the gearbox into 'C', for instance, (which admittedly denotes 'controlled efficiency' rather than 'comfort') and the gearbox will shift up as soon as is sensibly possible to keep the engine speed as low as possible, moving you off in second gear and engaging sixth as low as 37mph.
This is almost the first thing the Mercedes blurb tells you about the new transmission. Okay, so it does also mention the low rotational inertia of the wet-plate start-up clutch first, but the fact that this allows you to change gear more precisely and rapidly than with a conventional torque converter should be the headline news for a performance car's gearbox, not its efficiency.
Having said that, the four-mode gearbox does seem to be equally at home playing the full-on flappy-paddle mentalist (it even allows you to bounce off the rev limiter in manual mode without changing up) as it does doing the relaxed cruiser thing.
The styling seems to have a split personality, too. The front wings are 17mm wider than the standard car on either side of the bonnet, a front bumper with larger air intakes and AMG-only LED daytime running lights. There are also chunkier side skirts, a beefy(ish) rear bumper, square quad exhausts tips and bespoke 19-inch AMG alloys.
But despite all the muscle-saloon ephemera the overall effect is somehow less aggressive than you'd expect. Unless you park a more humble E-class next to an E63 your average passer-by, if they notice it at all, will simply see a mildly tweaked Stuttgart taxi. AMG enthusiasts will notice, however, and perhaps that's all that matters.
The E63 AMG's dual personality begins to make most sense, though, when you get behind the wheel. The chunky, angular interior might not have been majorly jazzed-up by AMG but that's not a particularly bad thing, because in everyday driving its sensibly laid-out, well-built nature makes it an easy and comfortable place in which to pass the time.
And the AMG tweaks that are there - comfortable but supportive electrically adjustable sports seats and a four-spoke AMG sports wheel with shift paddles - add an understated air of sportiness without compromising everyday comfort.
Trundling through busy weekday urban traffic, the first thing you notice is how relaxed the transmission feels - in its softest mode the E63 manages a passable waft, with the engine keeping smooth and quiet and the ride proving surprisingly supple despite the 19-inch alloys.
As the road opens up and the traffic thins out, your attention will turn to the rotary knob to the right of the stubby shift selector, and the three buttons below that. These form the AMG Drive Unit, and allow you to choose between four different gearbox modes, two different suspension settings and three ESP modes. All of which is, frankly, a bit of overkill, but it really does make quite a difference.
Faced with an empty and well-sighted B-road, all you need to do to transform the big Merc's behaviour is to flick the rotary knob into S+ for sharper, more reactive gearchanges, switch the dampers one setting harder, and pop the ESP into sport mode.
Now the old girl really hurls herself down the road with enthusiasm. The stiffer ride controls lateral and vertical body movements without wrecking the ride quality, the gearbox suddenly allows the big V8 to bellow its power out across the rev range rather than changing up at the first opportunity, and the ESP permits you the small amount of slip that makes you feel good about your driving but with the full knowledge that it will catch you should you become over-exuberant with your right foot.
Find yourself an empty piece of tarmac or take your E63 to a track, switch the ESP off completely and I defy you not to be smiling from ear to ear in the (short) time it will take to blitz the E63's tyres.
Mercedes was kind enough to book out the Top Gear test track at Dunsfold in Surrey for us to play with and, although the temptation to have a go at a Stig-style power lap was pretty major, it was easily overwhelmed by the lure of smoky slides. Well, okay, not smoky as there was a fair amount of water on the track, but the point is that, given enough space, the E63 becomes a lovely thing to fling about beyond its limits of grip. It's well balanced, the big bhp and wide, linear power band allow an amazing amount of adjustment on the throttle, while the faithful steering and long wheelbase make silly behaviour an eminently controllable activity.
So there you have it: the E63 is a comfy cruiser, a hoot to chuck down a B-road and a laugh on the track. So what if its looks are understated - that's a pretty good tick list for any self-respecting super-saloon, right? Well, yes, but there is one problem, and it's shaped like a Jaguar XFR. It would be hard to say which one is actually the better car without a back-to-back comparison, but the XFR is 50 quid shy of £10k cheaper than the Mercedes. And I would be willing to bet that the Mercedes isn't 10 grand better.