I have 2007 X3 3.0si. Since I got it, I have found that except when cruising on the highway (straight highways), I tend to use the sport mode most of the time and when I drive winding roads, I regularly use the manual mode for both down shifting for deceleration and having more torque around the turns. I think the key issue is allowing the car to warm up before getting hard on the accelerator and pushing the RPMs above 4 or 5K. BMW straight six engines thrive on high RPMs once warmed up and broken in.

I have driven the 328xi a number of times so I can understand why you would want to use the sport mode and manual--the engine which is lively at higher RPM seems a bit light on torque below 3000 RPM. I have also driven the 335xi and that one really does not need the sport mode, but even here, you will get a lot more punch as the lower gearing/higher RPMs of the sport mode will get the turbos spooling up faster. My X3 has plenty of torque throughout the RPM range, but it is a blast to zip past most cars at lower speeds and have that faster throttle response in the sport mode.