I own an '11 X5d with the 6spd but had a loaner 8spd '11 model while mine was getting programming updated and the oil change this past week. The 8spd transmission shifting was firm and responsive so no complaints on my part there. The thing I didn't care for was the fact that the transmission is shifting so much in stop and go traffic under normal acceleration in an effort to keep RPM's down and fuel mileage up with so many forward gears that it feels as though it is shifting between gears more often than engaged in any one gear which gives kind of a herky-jerky acceleration from stoplight to stoplight. Not necessarily a downside and I understand the mileage benefits, just an FYI.