Pressing the left button above the Trackball switches the mouse into Media Mode, which puts you in direct control over your media within iTunes or Windows Media Player (the only two players supported by the driver at this time). The left- and right-click buttons become Play/Pause and Stop, and the knob controls volume and track adjustments. The SlimBlade adds two extra clicks to access the media shortcuts: one click to switch modes, and one more to go back to navigation mode. Compared to the customizable buttons on the Logitech MX 1100, where you can set a single button to lower/raise volume or change tracks, this feature just requires too much effort to be considered a seamless operation. To Kensington's credit, a heads-up display is built into the driver to show you which mode you're in, in case you happen to lose track.
The button on the upper right side of the platform puts you in View Mode. In this case, turning the ball left and right zooms into the screen, effectively increasing the size of words and pictures on a document or Web page. Conveniently, the software also keeps a record of which Web sites you've zoomed into, even if you navigate away from the page. Again, the function requires two clicks: one to enter into View Mode, another to get back to Navigation mode. Designed for use with Web sites with tiny text, graphical documents, and word processing documents, the zoom feature is certainly convenient for the visually impaired, but we fail to see how this is more convenient than Apple's Vision Assistance feature, specifically the screen magnification setting. In fact, Apple takes the convenience a step further by offering the option to keep the cursor in the middle of the screen, automatically moving the cursor, or only moving it at the edge of a screen. (Windows also has a built-in magnification feature, though it's somewhat buried.) In contrast, the SlimBlade software keeps the cursor stationary, forcing you to scroll around to find what you're looking for.
In addition to suffering from iPhone Syndrome, where fewer buttons are never more, the Kensington SlimBlade Trackball lacks any kind of customizable settings. In other words, it doesn't give the user control over the program routed to each button, nor does it allow you to change the sensitivity of the scroll wheel, which places the SlimBlade Trackball behind even the most basic, stock mice. The added shortcuts are theoretically clever, but in practice they require more thought than it takes to simply switch applications and press the arrow key to change tracks. Die-hard trackball devotees might want to go with either of these basic Logitech models, which got high marks from CNET readers. For everyone else, we highly recommend you take a look at the Logitech MX 1100, which recently earned our Editors' Choice award for its best-in-class comfort and features.