This tip, which we were directed to by RIM's BlackBerry Connection newsletter, explains how to alter sensitivity of the trackball on the BlackBerry Pearl (8100). Here's what you do:

On the Home screen, go to Options -> Screen/Keyboard.

In the Trackball section, click Horizontal Sensitivity or Vertical Sensitivity to change the sensitivity level.


        The greater the number the
        higher the sensitivity level.

Press the Menu key and then select Save to set the new sensitivity levels.