* Driveability: The 650i's twin-turbocharged 4.4 litre V8 has but the barest hint of turbo lag - throttle response is near-instant.
There's a huge amount of low-down torque – 600Nm is on tap from as low as 1750rpm, and doesn't disappear until 4500rpm – and 300kW is available from 5500rpm to just shy of the 6500rpm redline. Those figures provide a wall of power under the toe; the 650i is seriously fast.
When the driving is more relaxed, the standard eight-speed automatic operates smoothly, but transforms in manual mode with super-quick shifts.
In ‘Sport’, shift-mapping is sharpened appreciably, although we noticed that the transmission won't hold gears against the redline during manual shifts.
* Refinement: The cabin is blissfully quiet save for the engine's well-muffled V8 burble. Extra layers in the fabric roof insulate the interior from outside noises, and refinement is on par with many hard-tops.
Top down and with windows up, there's minimal wind buffet at highway speeds. Windows down, conversations can still be had at 100km/h without shouting yourself hoarse.
* Suspension: The 650i gets active dampers and active rollbars, which automatically adjust to changes in road quality as well as the position of the Dynamic Driving Control.
In Comfort mode the ride is smooth and soft, while Normal and Sport modes are markedly stiffer.
In Sport mode the suspension is too stiff to properly dampen small bumps and corrugations, but body roll is minimal and grip is impressive.
The stability control cuts in before too much wheel slip occurs, but Sport+ mode allows a small amount of lateral slip - letting the back-end step out - for drivers who really want to connect with the drive.
The electric power steering is light and lacking a little in feedback. On the plus side, it feels direct, and, despite its size, the 650i is capable of changing direction very quickly.
* Braking: The 374mm front rotors and 345mm rear rotors are more than capable of shedding speed, and we couldn't get them to fade. An auto-hold function of the electronic parking brake also helps with hill starts.