As a reference point, BMW states the F12 650i in rear wheel drive configuration weighs 4520 pounds. So the addition of all wheel drive adds a not so insignifcant 153 pounds to the already heavy 4500 pound car. Imagine what the weight would bloat to if they included a convertible hardtop?
This being a 2012 model it does not have the updated and more powerful N63TU engine which will come in 2013 models. The standard 400 horsepower and 450 pound-foot of torque turbocharged V8 does fairly well considering the weight with 60 miles per hour coming in 4.4 seconds and 1/4 mile in email@example.com. Respectable but despite two turbos and a larger V8 motor this car would struggle to pull away from an E46 M3 on the highway. The E46 M3 that came out in 2001 with a 333 horsepower 3.2 liter six-cylinder. Where is the Efficient and Dynamic part again?
The car will get faster when it gets the 50 horsepower bump but that will only serve to mask its absurdly high curb weight.