Soft curves look right at home next to your Mac.

As a piece of hardware, the SlimBlade Trackball is nearly perfect. All of its modern curves lead to the red orb in the middle, making it comfortable and functional. Giant click and Control-click (aka left and right) buttons are easy targets in the front corners. Two back-corner buttons activate advanced navigation and iTunes controls. You can even scroll by twisting the trackball, without the need to reach for another wheel or button. Even though the software design disappoints (more on that in a moment)--you can’t customize any functions--we like this pointer overall.

To start, a quick software driver installation left us confused; where’s its System Preference pane? Instead of those typical settings, Kensington just adds an icon to the menubar to signify that the trackball is connected and the software is working. Forget all of the customized button functions in previous Kensington trackballs.

While we wanted to tweak a few options, the mandatory settings are useful in most situations. The upper-left button toggles into an iTunes-controlling mode, paralyzing the mouse temporarily. No matter which application is in the foreground, twists adjust the volume, left- and right-movements skip between tracks, the left button plays (or pauses) music, and the right button stops songs. But why the almost useless “stop?” Too bad you can’t reset its function. And only the volume control gives visual feedback; we wanted an option to superimpose song names onscreen when jumping ahead.

The upper-right button toggles into the view mode. In this case, mouse movement scrolls around documents, twists zoom, the left button sets the document to 100 percent zoom, and the right sets it to fit to the display width. These functions work in many applications: Photoshop, Firefox, Lightroom, and more. But without driver customization, you’re waiting on Kensington to add support for others, including Aperture and iPhoto.