Although I've only had my 650i for a week or so, I am already impressed with the quality and feel of such a high performance, luxury coupe. It has plenty of power and very stable handling. My last car was an '05 Porsche Carrera. This BMW is much more luxurous and as much fun to drive without all of the bumps of a much stiffer suspension. Beautiful lines, classy interior, and the iDrive isn't at all that hard to use once I spent some time with it. I'm very pleased with my choice.
I picked up an '07 650i coupe for $51K, plus trade in of a '99 M3 with 80K miles on it. The 650 is a delight (sure, you say, what wouldn't be compared to the rusty horse I'd been riding), and in unexpected ways. The seats envelope in a way superior to those in the 2009 MB CL I rented and are far superior to those in the Carerra. The engine sound is of elegant fortitude, the handling pugnacious when demanded but otherwise smooth and flat-out fun. The sports mode is a bit jerky at times, but darn quick off the line (the normal mode, which my wife dubs 'the macher mode,' is far less responsive to the pedal stomp yet very smooth). I feel very safe in it, although the A-pillar obscures a bit.
Went for a drive in the country last weekend and all I can say is WOW! Car was rock solid at 110 and when passing a car it was still pushing me back in the seat at 80. Has all the torque you would ever need. Soft leather seats and a well laid out interior. The exhaust rumble make you want to drive it. This car is a keeper.
The 650 has what BMW calls an "inherent characteristic." If you drive in "manual" shift mode the vehicle is prone to stuttering when coming to a stop. Imagine your head bobbing back and forth like a doll on the dashboard. The vehicle is also prone to severe lunges when driving in m1 (such as you might in a parking garage looking for a spot or while moving forward in a metered freeway on ramp) and to a lesser extent in automatic. The lunges are dangerous and you must drive defensively at 4 miles per hour. BMW states the problem is with the software-it thinks the engine is stalling and the computer gives the engine throttle. BMW won't fix the problem. Stay away from this vehicle.