[masmole]

It's actually more expensive to properly implement frameless door windows than with frames. The fit and finish tolerances at the factory are much higher for such designs and of course many cars like p-cars and bmws have to devise a slight electric window retraction during opening and closing.

There are many reasons why it's good: 1) reduced weight especially up high (lowered center of gravity), 2) style (the new $110k Mercedes CL vehicles have been using this design), 3) less chance of smacking yourself in the face with the upper corner of the door frame accidentally when opening/closing the door because the doors are much longer than in a sedans (I've seen it happen) 3) if done right, it doesn't create any more wind noise or filter out less road noise. I've noticed that my framed RS4 was much noisier by the A & B pillars than my frameless M3 coupe.