I am going to give my limited review of the 550i I justpicked up. Due to traffic, construction, etc, plus the fact that it is in the break in period, I did not use much in the way of throttle input, etc.
Ride is smooth, very smooth. In sport mode, it is a little bit tighter, but you don't lose the smooth feeling of the car, even over railroad crossings. Sport+ will wait until I have more experience with this car. As it is RWD and 450 ft-lbs of torque, it has more than 125 ft-lbs more than I am used to and 100 more HP. I want to be cautious and learn the car better before engaging all of the power or disengaging any of the nannies.
Engine is responsive - even given the limited throttle input, the engine was very responsive. Sticker says double VANOS and valvetronic. This could be a misprint by BMWNA, or it could be an engine difference, but that is unknown.
Transmission is touchy. If you blip the throttle, it stays in a higher gear for longer than I think it should, especially if you are slowing down (for instance, turning onto a street, then stopping at the next light)
There was no pull to the right observed. Steering was firm and felt responsive. I believe it has good road feel, providing good feedback from the road surface.
Cornering and handling capabilities are more than I will ever need. I am a fairly conservative driver, but I was able to take corners even faster than I could in my Lexus GS. Body roll was minimal with no squeeling
The multi-contour seats are amazing. I was able to find the perfect setting to drive. In previous cars, that has always been a slight compromise. Adjustable side bolsters would have been nice, but this was still a high A. One slight complaint is that the adjustable head bolsters don't quite line up with the way I sit in the drivers seat.
They took away the second USB in the glovebox for drivers with Nav, so that is missed. Also, I can not comment on the Nav as BMW was not able to provide the dealer with the activation code in time. This is a BMWNA problem.
I will upload pictures as I can.