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.
The engine - cool, confident rumbles; you just know this car will jam. And the body style. Some hate it; most love it. I've been repeatedly complimented on the look of the machine. The sound system is superb (though for my tastes it could use a bit more bass in the back). The seats: perfect.
The "wart" is a problem. It takes a while to master and it isn't intuitive (I understand many of the issues have been fixed with the '10 model). The nav system is great in theory, but if you make a mistake inputting an address, you must go back to start. Cool night vision feature never works well.