Commander is probably the only reason why I haven't sold my M3 yet, especially after the last updates. I did when I disabled it for excluding that the issues I encountered were its fault, and I wanted to crash the car.
Disables the speed limit chime, disables autopilot before you inadvertently exceed 140km/h when recovering from a phantom brake or another car decelerating before you before leaving your lane, gracefully and gradually enables standard acceleration when needing a "kickdown", reconnects autopilot,l when changing lanes (useful coupled with TACC for a seamless experience), connects to the LED stripe signaling turning lights, autopilot statuses including nag visual warnings, blind spot warnings... just have a look at the features on their website.
It's nice having the S3XY buttons. I only have two behind the wheel as index fingers triggers: one to restore the headlight flashing, the other to enable autopilot with one tap by keeping TACC on when disabling it after the idiotic changes.
The knob is only useful for right seat memories, it's the only reason why I don't remove it. It's very clumsy, because the buttons have no displays themselves (might be solved by new hardware) and thus their functions are displayed on the knob, display which gets lost once you enter a function, which requires turning the knob even for simple on/off operation - while pressing it acts as a back button. Very counter intuitive. The haptic feedback vibrates like a 1990 Nokia, has absolutely no punch and "instant" feeling.