SPORT MODE
 

What does really the Sport Button do? When I push it I can feel the car shake a fraction of a sec, but what exactly happens? I imagine the suspension becomes stiffer, gas pedal response might be better, although I don't see why it wouldn't be fast even with normal mode on. But what else?
I know this could be a really stupid question, but as a 10 day new owner of 4.8 xDrive with all possible packages, I'm curious to know what to expect and do I really have.
Thanks all!

The sport button just stiffens the suspension to further eliminate body roll. It does not re-map or adjust the throttle or transmission.

Are you sure about that? On most BMW's it does change the throttle map and drops the possibility of top gear, and allows redline shifts. X5 I dunno.

From the BMW USA site:

Sport mode.


Tune up: when sport mode is activated, engine output and driving dynamics take on sportier qualities, letting you enjoy your BMW's dynamic character at its peak.

Depending on which BMW model you drive, the sport mode can be activated by a touch of the "Sport" button on the central console. Immediately, your BMW feels even more dynamic: the electronic control units switch to sportier settings, making the engine more responsive and the suspension stiffer.
This increase in sports-style characteristics is accompanied by a reduction in powered assistance for the steering at low and medium RPMs for more direct and immediate steering, giving you an even closer sense of the character of the road.
In vehicles with automatic transmission or the Sequential Manual Gearbox (SMG), activating the sport mode (also known as Driving Dynamic Control) shortens gearshift times and makes the gearshift characteristic even more dynamic.

I'm pretty sure that Denalio is correct. The 2008 Owner's Manual is no help though. All it says is that

"You can choose between two types of chassis and suspension tuning.

Basic: The comfortable basic setting offers optimum comfort when traveling.

Sport: The sporty basic setting offers increased driving agility."

It does not appear that the description was written by a native English speaker so who knows exactly what it does...

Yea, in order to get a more sporty response from the transmission u need to move the stick over to"DS"

it does nearly nothing in my personal experience. ;)