Looks like this issue is specific to this transmission, not the engine or chassis. From this month's Bimmer Magazine, in a review by Mike Miller of the X3 28i:
"...Sport mode also starts the vehicle out from a stop in first gear instead of second, which brings me to my only drivetrain quibble: This transmission really rewards smooth driving and prefers an acceleration rate I'll charitably call conservative.
It may expect too much patience of the driver, especially in a metropolitan area where it isn't socially acceptable to motor away at a leisureley pace once the light turns green. Give it some gas and the X3 starts to move but not quickly enough. Tip in a bit more throttle and the transmission downshifts into first and off you go, spilling coffee on your shirt as it lunges forward. It's not consistent and the rate of acceleration seems to depend on the incline of the road as well as the degree and speed at which you add throttle
Using the transmission's Sport mode eliminated the issue at start-off but then made the subsequent shift into second more abrupt. The best shifting could be achieved by using Manual mode and shifting about 3,000 to 3,500 RPM which resulted in silky smooth gear changes notwithstanding a heavy foot on the gas pedal."
I couldn't have described it more perfectly. To me, this is a severe programming issue with this transmission and 6 cylinder engines. My friend with an X6 35i has the same thing, as does seemingly both 6 cylinder F10s. Doesn't seem like the 8 cylinder cars experience it as much or at all? It needs to be perfected. It has been written about in almost every review of the car, especially the long term tests (Edmunds, Motor Trend, etc.)
I am going to email Mike Miller to see if there is something he can do with his contacts within BMW to put pressure on them to fix this issue. Unlike Mike, who says "...I cannot emphasize enough that this minor complaint did not impair my enjoyment of the X3." I feel that it is very, very annoying and highly detracts from the enjoyment of the car. It's something I have to think about EVERY time I drive the car, and EVERY time I pull away from a stop. With my driving conditions in NoVA, DC, that is a LOT of times.
Let's see if we can ratchet up the pressure on BMW to fix this!!!
Sophisto Grau / Oyster - Black Nappa, Anthracite Wood Gone but not forgotten.
Heaven is where the police are British, the cooks are French, the cars are German, the lovers are Italian and it is all organised by the Swiss.
Hell is where the police are German, the cooks are English, the cars are French, the lovers are Swiss, and it is all organised by the Italians