This is also supposed to improve the roll. Often, you need to drag an item across the screen. This is done by holding down the left button while moving the pointer, a difficult act of coordination. The left button will act like it is being held until the click-lock button is pressed again. This is the first time that the drag procedure has been easy, and is a major benefit of trackballs.
Some people complain that their wrists gets sore from resting on the desktop.
Very recently, Kensington has been offering free wrist rest pads when users send in their registration. Other users will need to contact their office supply store. Cut off and use the last five inches. Put a mouse pad under the trackball. The thicker and softer, then better.