One nice aspect of the top is that it can be raised or lowered while the car is moving, at speeds up to 25 mph. One not-so-nice aspect is that the top's design makes for major blind spots. The workaround, of course, is expensive electronics. A backup camera (cleverly hidden under the roundel badge on the trunk) is standard, but you might also consider adding the Driver Assistance Package, with its top-view and cross-view cameras and blind-spot warning; it also includes lane departure warning, a head-up display, and automatic high beams).
Turbocharging continues its march through the BMW lineup, as the 4.8-liter naturally aspirated V-8 is here again booted out in favor of the 4.4-liter turbo, code-named N62, that we've seen already in the X5, X6, 5-series, and 7-series. Fortified with two turbochargers, the smaller engine brings a lot more power to the party: 400 hp versus 360 hp, and it's available lower in the rev range, at 5000-6400 rpm. Torque jumps from 360 lb-ft at 3400 rpm to 450 lb-ft, and again it's more accessible, from 1750 to 4500 rpm. Power delivery is beyond reproach, and you'd never discern that this engine was turbocharged. And yet, acceleration doesn't feel as explosively quick as the numbers suggest (0 to 60 mph in 4.9 seconds, more than half a second better than the previous 650i), perhaps because the car is so heavy. At over 4500 pounds, it has gained some 250 pounds over the not-so-lithe previous edition. Practically speaking, though, you're never wanting for power. On our test drive, the 650i made quick work of the 40-to-80-mph sprint, when overtaking on two-lane roads outside Capetown (where the courteous South African drivers regularly astonished the visiting American press with their practice of moving over onto the shoulder to facilitate a pass, and even signaling when it was safe to do so).